SOUTH COAST AIR QUALITY MANAGEMENT DISTRICT

SOUTH COAST AIR QUALITY MANAGEMENT DISTRICT

5 YEAR NETWORK ASSESSMENT 

July 2010

Prepared by

Rene M. Bermudez

Principal Air Quality Instrument Specialist

Philip M. Fine

Atmospheric Measurements Manager
Air Quality Monitoring Network Plan – July 2010

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Table of Contents

Page

I Introduction ............................................................................................. 1

II Site Assessments ............................................................................... 21

III Network Assessment ............................................................................ 44

IV Potential AQMD Network Changes ......................................................... 86
1

I. INTRODUCTION

A periodic Network Assessment of the Ambient Air Monitoring Network is required by Federal 

Regulations as a key tool to help ensure that criteria pollutants are measured in important 

locations and that monitoring resources are used in the most effective and efficient manner to 

meet the needs of multiple stakeholders. Network assessments help identify new data needs and 

associated technologies, find opportunities for consolidation of individual sites into 

multi-pollutant sites, and identify geographic areas where network coverage should be increased 

or decreased based on changes in the population and/or emissions. The Environmental 

Protection Agency (EPA) requires that local agencies perform an assessment of the air quality 

surveillance system every 5 years to determine, at a minimum, if the network meets the 

monitoring objectives defined in Title 40, Part 58, Section 10 of the Code of Federal Regulations

(40 CFR § 58) Appendix D, whether new sites are needed, whether existing sites are no longer 

needed and can be terminated, and whether new technologies are appropriate for incorporation 

into the Ambient Air Monitoring Network. This report describes the assessment of the Ambient 

Air Monitoring Network operated by the South Coast Air Quality Management District (AQMD) 

and fulfills the requirements for a periodic network review as listed in 40 CFR § 58.10. 

Regulation requires that the report be submitted to the EPA by July 1 2010. 

SOUTH COAST AQMD HISTORY

Early efforts to control air pollution in California began in Los Angeles with legislation 

proposing counties establish Air Pollution Control Boards. The proposed legislation was 

approved and signed into law on June 10, 1945 and the Los Angeles County Air Pollution 

Control District was established in October 1947. Orange County, San Bernardino, and 

Riverside formed Air Pollution Control Districts by 1957. Realizing that air pollution was a 

regional problem, the four counties merged to form the South Coast AQMD in 1977. 

Geographically, South Coast AQMD encompasses 10,750 square miles and is located within the 

South Coast Air Basin (SCAB), which is the second most populated area in the United States. 

Southern California consistently records the highest levels of ozone (O3) and particulates in the 

nation. As the local air pollution control agency, South Coast AQMD is responsible for 

controlling air quality emissions from various sources to meet National Ambient Air Quality 

Standards (NAAQS) as well as ambient air quality standards established by the California Air 

Resources Board (CARB). Every three years an Air Quality Management Plan is developed and 

adopted by the South Coast AQMD Board, which describes what actions will be taken to bring 

the SCAB into compliance with State and Federal clean air standards. To assess compliance 

with State and Federal standards, a surveillance network of 40 permanent air monitoring sites are 

maintained to measure criteria pollutants. The air quality data collected by the surveillance 

network is used for comparison to air quality standards, developing control strategies and 

regulations to meet those standards, and to provide public information on current and forecasted 

air quality.

South Coast AQMD operates 40 permanent air monitoring sites in the SCAB and a portion of the 

Salton Sea Air Basin in Coachella Valley. This area includes Orange County and the non-desert 

portions of Los Angeles, Riverside, and San Bernardino Counties. South Coast AQMD also 

operates numerous temporary monitoring sites for shorter-term objectives such as air toxic 

studies, community-based monitoring, and compliance with air quality regulations. 
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MONITORING NETWORK HISTORY

The earliest air monitoring station was operated by the Los Angeles County Air Pollution 

Control District at 5201 Santa Fe St. before being relocated to the agency's headquarters at 434 

South San Pedro in 1955. The oldest monitoring location still in existence is located in Azusa 

and opened in 1957. The newest permanent site was added in 2008 in Compton to replace the 

Lynwood air monitoring location. Table 1 provides a list of monitoring locations, EPA Air 

Quality System (AQS) site codes, and the pollutants measured at each site. Table 2 provides 

monitoring objectives and the spatial scale of representativeness for monitors at each site. Table 

3 describes the monitoring purpose for monitors at each site. Table 4 describes the monitoring 

objective, purpose, and spatial scale for continuous particulate analyzers at each site. Monitoring 

objectives are defined as:

Background Level monitoring is used to determine general background levels of air 

pollutants as they enter the SCAB.

High Concentration monitoring is conducted at sites to determine the highest concentration 

of an air pollutant in an area within the monitoring network. A monitoring network may 

have multiple high concentration sites (i.e., due to varying meteorology year to year).

Pollutant Transport is the movement of a pollutant between air basins or areas within an

air basin. Transport monitoring is used to assess and mitigate upwind areas when a 

transported pollutant affects neighboring downwind areas. Also, transport monitoring is 

used to determine the extent of regional pollutant transport among populated areas and to 

rural areas.

Population Exposure monitoring is conducted to represent the air pollutant concentrations 

a populated area is exposed to.

Representative Concentration monitoring is conducted to represent the air quality 

concentrations for a pollutant expected to be similar throughout a geographical area. These 

sites do not necessarily indicate the highest concentrations in the area for a particular 

pollutant.

Source Impact monitoring is used to determine the impact of significant sources or source 

categories of air quality emissions on ambient air quality. The air pollutant sources may be 

stationary or mobile. 

Trend Analysis monitoring is useful for comparing and analyzing air pollution 

concentrations over time. Usually, trend analysis show the progress or lack of progress in 

improving air quality for an area over a period of many years.

Site Comparison monitoring is used to assess the effect on measured pollutant levels of 

moving a monitoring location a short distance (usually less than two miles). Some 

monitoring stations become unusable due to development, change of lease terms, or 

eviction. In these cases, attempts are made to conduct concurrent monitoring at the old and 

new site for a period of at least one year in order to compare pollutant concentrations.
3

Real Time Reporting/Modeling is used to provide data to the EPA’s AIRNOW system, 

which reports conditions for air pollutants on a real time basis to the general public. Data 

is also used to provide accurate and timely air quality forecast guidance to residents of the 

South Coast basin.

Multiple purposes for measuring a pollutant at a particular site are possible. There is some 

overlap between monitoring objectives as defined by the EPA and given in Table 2, and the 

monitoring purposes provided in Table 3.

A brief description of the network for each criteria pollutant monitored and monitoring program 

is provided below:

Ozone

The South Coast AQMD operates 30 sites where ozone (O3) measurements are made as 

part of the Air Monitoring Network. Figure 2 in Section III shows the spatial distribution 

of these sites.

Carbon Monoxide

Ambient carbon monoxide (CO) monitors measure concentrations at 26 locations. 

Figure 5 in Section III shows the spatial distribution of these sites.

Nitrogen Dioxide

The nitrogen dioxide (NO2) network consists of 26 sites. These sites are mostly located 

in areas of highest NO2 concentration. The spatial distribution of NO2 monitors is 

shown in Figure 7, Section III.

Sulfur Dioxide

Sulfur dioxide (SO2) monitors are located at 7 sites. Figure 9 in Section III shows the 

spatial distribution of the sites.

Particulate Lead

Total suspended particulate (TSP) lead (Pb) measurements are collected at 19 sites as part 

of the network. Five sites are source-oriented and the remaining 10 sites are populationoriented. The spatial distribution of these sites is shown in Figure 11, Section III.

PM10

Size-selective inlet high volume samplers are operated at 22 sites to meet the 

requirements for PM10 Federal Reference Method (FRM) sampling. Of the 22 sites, 13 

also include continuous PM10 analyzers. Figure 13 in Section III shows the spatial 

distribution of the sampling sites.

PM2.5

A network of 17 FRM samplers was first implemented in January 1999. Since then, the 

network has expanded to include 20 sites depicted in Figure 16, Section III and listed in 

Table 5. Continuous PM2.5 Met One Beta Attenuation Monitors (BAMs) were first 

deployed in 2001. Sixteen continuous PM2.5 monitors are now operating in the Basin.
4

PM2.5 speciation sampling is also a part of the South Coast AQMD PM2.5 monitoring 

program. The network includes two Speciation Trends Network (STN) samplers and 

four permanent South Coast AQMD speciation monitoring locations.

The following is a brief description of specific programs that are operated within the Ambient 

Air Monitoring Network:

Photochemical Assessment Monitoring Stations (PAMS)

The PAMS network was initiated in June 1994 and consists of 7 air monitoring locations. 

PAMS are used to collect data for a target list of Volatile Organic Compounds (VOCs), 

Nitrogen Oxides (NOx), Reactive Oxides of Nitrogen (NOy), O3, and meteorological 

measurements. The PAMS network was established to provide information about the 

effectiveness of control strategies, emissions tracking, trends, and exposure. To address 

regulatory changes, site-specific observations from the recent National PAMS Network 

Assessment, and to address potential synergies between programs, South Coast AQMD

made changes in June 2009 to the PAMS monitoring network based on specific 

recommendations:

 Burbank was reclassified from Type 2/1 to Type 2. This change addressed the 

National PAMS Network Assessment observation that Burbank should be 

reclassified to a Type 2 precursor site. The recommendation is consistent with the 

heavily urbanized/industrialized area, which is impacted by high levels of O3 

precursor emissions. 

 Santa Clarita was reclassified as Type 3 from Type 2. Although the National 

PAMS Network Assessment observed that Santa Clarita was consistent with a 

Type 2 site, recent data was more consistent with a Type 3 maximum O3 

concentration site rather than a Type 2 O3 precursor site.

 Banning was relocated to Los Angeles (Main). The National PAMS Network 

Assessment observed that Banning had the lowest O3 concentrations of all the 

Type 2 sites and should be reclassified to a Type 3 or 4 site. Instead, to create 

synergies between programs, South Coast AQMD relocated the Banning PAMS 

site to the Los Angeles (Main) site as Type 2. This satisfies the EPA 

recommendation for use of the same monitoring platform and equipment to meet 

the objectives of multiple programs. Los Angeles (Main) is also a National Air 

Toxics Trends Station (NATTS), a future National Core-Multi-pollutant 

Monitoring Station (NCore), and an STN site.

 Azusa was reclassified from Type 3 to Type 2. This proposed change addresses 

the National PAMS Network Assessment observation that Azusa has high VOC

and NOx concentrations, with lower O3 concentrations. The site now more 

closely resembles a Type 2 O3 precursor site.

 Upland was relocated to the Rubidoux site. The National PAMS Network 

Assessment observed that Upland was no longer consistent with a Type 4 site and 

recommended reclassification to Type 3. South Coast AQMD relocated the 

Upland PAMS site to Rubidoux as a Type 3 location where synergies can be 

created among the NATTS, NCore, and the STN programs.
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 LAX Hastings and Pico Rivera remained unchanged.

Currently, manual VOC canisters are in operation at the Azusa, LAX Hastings, 

Rubidoux, Los Angeles (Main), and Santa Clarita air monitoring stations. During the 

intensive season from July 1 until September 30, VOC canisters are run every three hours 

for a period of twenty-four hours every 3rd day and a twenty-four hour sample is run 

every 6th day. During the non-intensive season from October 1 through June 30, twentyfour hour VOC canister samples are run every 6th day.

At Los Angeles (Main) and Santa Clarita air monitoring stations, during the intensive 

season from July 1 until September 30, carbonyl samples are run every three hours for a 

period of twenty-four hours every 3rd day and a twenty-four hour sample is run every 6th 

day. During the non-intensive season from October 1 through June 30, twenty-four hour 

carbonyl samples are run every 6th day.

Automated gas chromatography flame ionization detector (GC\FID) VOC systems are in 

operation at the Pico Rivera and Burbank air monitoring stations. During the intensive 

sampling season from July 1 until September 30, the GC\FID is run to collect 3-hour 

samples and twenty-four hour VOC canisters are run every 6th day. Like the other 

PAMS sites, carbonyl samples are run every three hours with one additional twenty-four 

hour sample run every 6th day. During the non-intensive season from October 1 through 

June 30, the GC/FID is idle and twenty-four hour VOC canister samples are run every 6th 

day and twenty-four hour carbonyl samples are run every 6th day. Rubidoux is a 

collocated site for VOC canister sampling and Pico Rivera is a collocated site for VOC 

canister and carbonyl sampling.

The first South Coast AQMD upper air meteorological monitoring station was 

established at Los Angeles International Airport (LAX) in 1994. Subsequent upper air 

stations include Ontario International Airport (ONT) installed in 1996, Moreno Valley 

(MOV) installed in 2001 at the Moreno Valley Municipal Water Treatment Plant in 

Riverside County, Irvine installed at the University of California Research and Extension 

Center in 2006, and Pacoima at Whiteman Airport during May 2007. The upper air 

stations use a combination of remote sensing and surface meteorological instrumentation, 

including the Vaisala (formerly Radian/URS) LAP-3000 radar wind profiler with a Radio 

Acoustic Sounding System (RASS), the Atmospheric Systems Corporation (formerly 

AeroVironment Inc.) mini Sodar acoustic wind profiler, and tower-mounted 

meteorological measurements of wind, pressure, temperature, relative humidity, solar 

radiation and ultraviolet radiation.

The PAMS network monitoring objectives and requirements are summarized in Table 6.

NATTS

The NATTS program was developed to fulfill the need for long-term hazardous air 

pollutant (HAP) monitoring data of consistent quality nationwide. South Coast AQMD

has conducted several air toxics measurement campaigns in the past, which demonstrated 

the variety and spatial distribution of air toxics sources across SCAB. A single air toxics 
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measurement site cannot reflect the levels and trends of air toxics throughout the basin. 

For this reason, two NATTS sites are used to characterize the SCAB’s toxics levels. The 

first site is a central urban core site in Los Angeles that reflects concentrations and trends 

due primarily to urban mobile source emissions. A second, more rural, inland site at 

Rubidoux captures the transport of pollutants from a variety of upwind mobile and 

industrial sources in the most populated areas of the air basin. NATTS monitoring began 

in February 2007 and continues at the Los Angeles (Main) and Rubidoux air monitoring 

sites. During April 2010, a system audit was conducted by the EPA, which assessed the 

South Coast AQMD NATTS program. The audit found no major issues with the 

operation of the network but recommended implementation of blanking and low level 

concentration challenge samples. Blanking will be implemented in 2010 and low level 

challenge samples will be implemented in 2011.

NCore

In October 2006, the EPA issued amendments to ambient air monitoring regulations for 

criteria pollutants. One of the most significant changes in regulations was the 

requirement to establish NCore stations. These stations provide pollutant data at much 

lower detection limits than the existing air monitoring network. NCore monitoring 

regulations require that South Coast AQMD make NCore stations operational by 

January 1, 2011. To meet this goal, South Coast AQMD has installed trace level 

analyzers for CO, NOy, SO2, and Continuous FEM BAM PM2.5 in Rubidoux and Los 

Angeles (Main), both of which are existing STN and NATTS sites.

NETWORK ASSESSMENTS

Regulatory Requirements

The earliest air monitoring sites in the United States were established over 50 years ago 

with sites added to the national network as needed to fulfill Federal monitoring 

requirements and other objectives. Since the time of inception, air quality, population, 

and behaviors have changed, and there is a general need for re-evaluation of the overall 

network design and objectives. Recognizing this need, the U.S. EPA finalized an 

amendment to the ambient air monitoring regulations on October 17, 2006 to address the 

issue. In the amendment, the U.S. EPA required State and local air monitoring agencies 

to conduct a network assessment once every five years, with the first assessment due by 

July 1, 2010.

The state or where applicable local agency shall perform and submit to 

the EPA Regional Administrator an assessment of the air quality 

surveillance system every 5 years to determine, at a minimum, if the 

network meets the monitoring objectives defined in 40 CFR § 58 

Appendix D, whether new sites are needed, whether existing sites are no 

longer needed and can be terminated, and whether new technologies are 

appropriate for incorporation into the Ambient Air Monitoring Network. 

The Network Assessment must consider the ability of existing and 

proposed sites to support air quality characterization for areas with 

relatively high populations of susceptible individuals, and for any sites 
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that are being proposed for discontinuance. The assessment must also 

consider the effect on data users other than the agency itself, such as 

nearby States and Tribes or health effects studies. For PM2.5, the 

assessment must also identify needed changes to population-oriented 

sites. The state or where applicable local agency must submit a copy of 

this assessment along with a revised annual network plan to the Regional 

Administrator. (40 CFR § 58.10d 236) 

In general, air monitoring networks must be designed to meet three basic objectives 

according to 40 CFR § 58. First, they must provide air pollution data to the general 

public in a timely manner. Second, they must support compliance with ambient air 

quality standards shown in Table 7, and third, they must support research studies on 

health effects assessments. In order to achieve these goals, networks must meet the 40 

CFR § 58 Appendix D, Network Design, and Appendix E, Probe Siting Criteria.

Network Design Criteria

Ambient air monitoring network design is specified by U.S. EPA and include monitoring 

objectives and general criteria, as outlined in 40 CFR § 58 Appendix D. Each objective 

is related to a specific type of air monitoring site, and air monitoring networks must be 

designed for each criteria pollutant and must meet specific objectives. Monitoring 

objectives and corresponding scales of representativeness are shown in Table 8.

Minimum Number of Sites

As a general requirement, the U.S. EPA specifies the minimum numbers of sites required 

in a network based on the latest census population data and design value concentrations 

for specific criteria pollutants. The minimum number of O3 sites required is based upon 

the Metropolitan Statistical Area (MSA) population and the most recent 3-year design 

value as shown in Table 9. As of July 2009, there were no minimum requirements for the 

number of CO, NO2, and SO2 monitoring sites in an air monitoring network, other than 

NCore requirements. New regulations for NO2 and SO2 require minimum numbers of 

monitoring locations taking effect in 2013, but they will not be addressed in this 

assessment. Local agencies are required to conduct ambient air Pb monitoring taking into 

account:

 Pb sources which are expected or have been shown to contribute to a maximum 

Pb concentration in ambient air in excess of the NAAQS.

 The potential for population exposure and logistics. 

At a minimum, there must be one source oriented SLAMS site located to measure the 

maximum Pb concentration in ambient air resulting from sources of Pb, which emit 1.0 or 

more tons per year based on the latest National Emission Inventory (NEI) or other 

justifiable methods or data. Local Agencies are also required to conduct Pb monitoring 

in each Core Based Statistical Area (CBSA) with a population equal to or greater than 

500,000 people. At a minimum, there must be one non-source oriented SLAMS site 

located to measure neighborhood scale Pb concentrations in urban areas impacted by reentrained dust from roadways, closed industrial sources of Pb, hazardous waste sites, 
8

construction and demolition projects and other fugitive sources of Pb. The number of 

PM10 sites required is based upon MSA population data and shown in Table 10. The 

number of PM2.5 sites required is based upon MSA population data and shown in Table 

11. The final number of sites in a network is subject to U.S. EPA Regional Administrator 

approval via the Annual Network Plan.

Probe Siting Criteria

Once a site has been selected based on monitoring objective and spatial scale, the site 

must also meet specific siting criteria for each spatial scale and each pollutant as 

specified in 40 CFR § 58 Appendix E. These criteria include the placement of the 

pollutant measuring device inlet probe, spacing from minor sources of pollution, spacing 

from obstructions to the monitoring probe, spacing from trees, spacing from roadways, 

probe material and residence time.

Horizontal and Vertical Placement

Inlet probes must be placed both horizontally and vertically so that at least 90 percent of 

the area over which pollutants are being measured and averaged is 1 meter (m) from 

walls or any supporting structure. For measurement of particulates, a minimum of 2 m is 

required. Inlet probes must also be placed between 2 m and 15 m above the ground level 

for all criteria pollutants at the neighborhood scale. Particulate probe inlets at middle and 

micro scale are to be between 2 m and 7 m above ground level. Near roadway, and CO 

micro scale measurements are to be 3 +/- 1⁄2 m above ground level. A summary of 

horizontal and vertical placement is shown in Table 12.

Spacing from Minor Sources

Spacing requirements are dependent upon the monitoring objective. If the objective is to 

measure the impact of a stationary source’s primary pollutant emissions, then the probe 

may be located close to the source and be classified as a micro-scale site. A micro-scale 

site typically represents an area up to 100 m in size. If the objective is to measure 

pollutants over a larger area such as a neighborhood or city, then the monitoring location 

should be located away from minor sources of pollutants so as not to impact air quality 

data collected at the site. Particulate matter sites should not be located in unpaved areas 

where windblown dust can influence data collected. Special attention should be placed 

on horizontal and vertical probe placement from furnace or incineration flues to prevent 

scavenging of O3 by NO and O3 reactive hydrocarbons. 

Spacing from Obstructions

Buildings and other obstacles may scavenge SO2, O3, or NO2 and restrict airflow for any 

pollutant measured. To prevent this influence, the probe must have unrestricted airflow 

and be located away from obstacles. The distance from an obstacle to the probe should 

be twice the height that the obstacle protrudes above the inlet. For particulate sampling, a 

minimum of 2 m separation is required between monitors, walls, parapets, and structures.

Spacing from Trees

Trees can scavenge SO2, O3, and NO2 by adsorption and provide a surface for particle 

deposition. Trees also act as obstructions and special attention should be made to adhere 
9

to correct spacing. To reduce interference, the probe inlet should be at least 10 m from 

the drip line of the tree. For micro-scale sites, no trees should exist between the probe 

inlet and the source being measured. 

Spacing from Roadways

O3 and NO2 in particular are susceptible to interference from roadway emissions. When 

siting monitors for neighborhood scale and urban scales, it is important to minimize 

roadway interference. Recommended spacing from roadways for O3, NO2, CO, and PM 

samplers are summarized in Tables 13, 14, and Figure 1. Recent requirements for microscale NO2 monitoring near roadways are not addressed in this assessment.

EPA Guidance and Memos

To facilitate the Network Assessment, the EPA issued guidance for local air quality 

agencies. During March 1998, the EPA Office of Air Quality Planning and Standards 

(OAQPS) issued State and Local Air Monitoring Stations (SLAMS), National Air 

Monitoring Stations (NAMS), and PAMS Network Review Guidance. Guidance 

advocated examination of compliance with Network Design Criteria, monitoring 

objectives, and minimum number of sites required. Guidance also recommended 

examination of 40 CFR § 58 Appendix E Probe Siting Criteria. In February 2007, the 

EPA issued Ambient Air Monitoring Network Assessment Guidance, which included 

analytical techniques for assessments of Ambient Air Monitoring Networks. In the 

guidance, the EPA summarized the context of network assessments, provided an 

overview of requirements in 40 CFR § 58, and an overview of the assessment process. 

The EPA provided steps in the assessment process and technical approaches including 

identification of monitoring needs, correlation analysis, and population change in order to 

assess high and low value monitors. The final step in the guidance was to suggest 

changes to the network, obtain input from State, Federal, and local stakeholders, and 

revise recommendations based on input. 

EPA Tools

To supplement guidance, the EPA presented an overview of the network assessment

process at the 2009 National Ambient Air Monitoring Conference. Training focused on 

the process of conducting network assessments, providing guidance on analytical 

techniques used for assessments, and emphasized the goal of identifying and removing 

low value monitors such that resources can be re-allocated to areas that are underrepresented. To further aid in the process, the following tools were made available that 

are used in this analysis:

Population Animation

The population animation tool is a Google Earth display that shows the change in 

population over 19 years relative to the 1990 population at the census tract level. 

Accompanying the population changes are the monitoring network changes from 

1990 to 2008. The sites will be displayed as either black circles or gray triangles 

representing active and inactive sites, respectively. Clicking on a site gives 

details of the sites start and end year. The animation serves as clear example of 

how populations have changed within the country over the past 19 years and how 

the monitoring networks have evolved to serve those shifting populations. In 
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many cases around urban areas across the country, the population has shifted 

away from the urbanized core to the suburbs and the monitoring networks have 

not evolved to take into account this change. 

Correlation Matrix Analysis

The Correlation Matrix Analysis shows the correlation, relative difference, and 

distance between pairs of sites within a monitoring network. The purpose of the 

analysis/tool is to provide a means of determining possible redundant sites that 

could be removed if pollution trends in that area are captured adequately by a 

nearby site. 
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TABLE 1 Ambient Air Monitoring Locations

Location AQS No. Pollutants Monitored Start Date

Anaheim 060590007 CO,NO2,O3,PM10,PM2.5 08/01

ATSF (Exide) 060371406 Pb 1/99

Azusa 060370002 CO,NO2,O3,PM10,PM2.5,SO4 01/57

Banning Airport 060650012 NO2,O3,PM10, PM2.5 04/97

Big Bear 060718001 PM2.5 02/99

Burbank 060371002 CO,NO2,SO2,O3,PM10,PM2.5 10/61

Closet World (Quemetco) 060371404 Pb 10/08

Compton 060371302 CO,NO2,O3,Pb,PM2.5 01/04

Costa Mesa 060591003 CO,NO2,SO2,O3 11/89

Crestline 060710005 O3,PM10 10/73

Fontana 060712002 CO,NO2,SO2,O3,PM10,PM2.5,SO4 08/81

Glendora 060370016 CO,NO2,O3,PM2.5,PM10 08/80

Indio 060652002 O3,PM10,PM2.5 01/83

La Habra 060595001 CO,NO2,O3 08/60

Lake Elsinore 060659001 CO,NO2,O3,PM2.5,PM10 06/87

LAX Hastings 060375005 CO,NO2,O3,PM10,Pb,SO4 04/04

Long Beach (North) 060374002 CO,NO2,SO2,O3,PM10,PM2.5,Pb,SO4 10/62

Los Angeles (Main St.) 060371103 CO,NO2,SO2,O3,PM10,Pb,PM2.5,SO4 09/79

Mira Loma (Jurupa)2

060650004 CO,NO2,O3,PM10 10/93

Mira Loma (Van Buren) 060658005 CO,NO2,O3,PM10,PM2.5 11/05

Mission Viejo 060592022 CO,O3,PM10,PM2.5 06/99

Norco 060650003 PM10 12/80

Ontario Fire Station 060710025 PM10,PM2.5 01/99

Palm Springs 060655001 CO,NO2,O3,PM10,PM2.5 04/71

Pasadena 060372005 CO,NO2,O3,PM2.5,SO4 04/82

Perris 060656001 O3,PM10 05/73

Pico Rivera #2 060371602 CO,NO2,O3,Pb,PM2.5,SO4,PM10 09/05

Pomona 060371701 CO,NO2,O3 06/65

Redlands 060714003 O3,PM10 09/86

Rehrig (Exide) 060371405 Pb 11/07

Reseda 060371201 CO,NO2,O3,PM2.5 03/65

Riverside (Magnolia) 060651003 CO,Pb,PM2.5,SO4 10/72

Rubidoux 060658001 CO,NO2,SO2,O3,PM10,Pb,PM2.5,SO4 09/72

San Bernardino 060719004 CO,NO2,O3,PM10,Pb,PM2.5 05/86

Santa Clarita 060376012 CO,NO2,O3,PM10,PM2.5 05/01

South Long Beach 060374004 PM10,Pb,PM2.5,SO4 06/03

Temecula1

TBD O3, PM2.5

Uddelholm (Trojan Battery) 060371403 Pb 11/92

Upland 060711004 CO,NO2,O3,Pb,PM2.5,PM10,SO4 03/73

Van Nuys Airport 060371402 Pb 1/10

West Los Angeles 060370113 CO,NO2,O3,SO4 05/84

1

Site to begin operation in 2010

2

Site to be closed in 2010 or 2011
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TABLE 2 FRM/FEM Criteria Pollutant Monitoring Objective and Spatial Scales

MONITORING OBJECTIVE SPATIAL SCALE

HC – High Concentrations MI – Microscale

RC – Representative Concentrations MS – Middle Scale

IM – Impact NS – Neighborhood Scale

BL – Background US – Urban Scale

Location CO NO2 SO2 O3 PM10 PM2.5 Pb

Anaheim NS/RC US/RC NS/RC NS/RC NS/RC

ATSF (Exide) MI/IM

Azusa NS/RC US/RC US/HC NS/RC NS/RC

Banning Airport NS/RC NS/RC NS/RC

Big Bear NS/RC

Burbank NS/HC NS/RC NS/RC US/HC NS/RC NS/RC

Closet World (Quemetco) MI/IM

Compton MS/HC MS/RC NS/RC NS/RC NS/RC

Costa Mesa NS/RC NS/RC NS/RC NS/RC

Crestline NS/HC NS/RC

Fontana NS/RC US/RC NS/RC US/RC NS/HC NS/RC

Glendora NS/RC NS/RC NS/HC

Indio NS/RC NS/HC NS/RC

La Habra NS/RC US/RC NS/RC

Lake Elsinore NS/RC NS/RC NS/RC

LAX Hastings MS/RC MS/RC NS/RC MS/RC NS/RC NS/RC

Long Beach (North) MI/HC MS/RC NS/HC MS/RC MI/RC NS/HC MI/RC

Los Angeles (Main St.) NS/RC NS/HC NS/RC NS/RC NS/RC NS/HC NS/RC

Mira Loma (Jurupa)

2 NS/RC NS/RC NS/RC NS/HC

Mira Loma (Van Buren) NS/RC NS/RC NS/RC NS/HC NS/RC

Mission Viejo NS/RC NS/RC NS/RC NS/RC

Norco NS/RC

Ontario Fire Station NS/HC NS/RC

Palm Springs NS/RC NS/RC NS/RC NS/RC NS/RC

Pasadena MS/RC MS/HC NS/RC NS/RC

Perris NS/RC NS/RC

Pico Rivera #2 NS/RC NS/HC NS/HC NS/RC NS/RC

Pomona MI/RC MS/RC MS/HC

Redlands NS/RC NS/RC

Rehrig (Exide) MI/IM

Reseda NS/RC US/RC US/HC NS/RC

Riverside MI/HC US/RC NS/RC MI/HC

Rubidoux MS/RC US/RC NS/RC US/HC NS/HC NS/HC NS/RC

San Bernardino MS/RC US/RC NS/HC NS/HC NS/RC NS/RC

Santa Clarita NS/RC NS/RC US/HC NS/RC NS/RC

South Long Beach NS/HC NS/RC NS/HC

Temecula1

Uddelholm (Trojan Battery) MI/IM

Upland NS/RC NS/RC NS/RC NS/RC

Van Nuys Airport MI/IM

West Los Angeles NS/RC MS/HC MS/RC

1

Site to begin operation in 2010

2

 Site to be closed in 2010 or 2011
13

TABLE 3 FRM/FEM Criteria Pollutant Monitoring Purposes

MONITORING PURPOSE

BK – Background Level RC – Representative Concentration

HC – High Concentration SPM – Special Purpose Monitoring

TP – Pollutant Transport TR – Trend Analysis

EX – Population Exposure CP – Site Comparisons

SO – Source Impact

Location CO NO2 SO2 O3 PM10 PM2.5 Pb

Anaheim TR TR/RC TR TR TR/EX

ATSF (Exide) SO

Azusa TR TR/RC TR TR TR/EX

Banning Airport TP/RC TP TP

Big Bear EX/SO/TP

Closet World (Quemetco) SO

Burbank TR TR/RC TR TR TR TR/EX

Compton TR/HC TR/RC TR/RC EX/RC EX

Costa Mesa RC TR/RC TR RC

Crestline HC TP/RC

Fontana RC TP/RC TR RC HC EX/TP

Glendora RC TR/RC HC

Indio TP HC TP/EX

La Habra RC TR/RC RC

Lake Elsinore TP/RC TP/RC TP/RC

LAX Hastings BK BK BK BK BK BK

Long Beach (North) HC TR/RC TR/HC TR TR/RC EX/HC EX

Los Angeles (Main St.) SO/RC SO/HC TR TR/RC TR/RC EX/HC EX

Mira Loma (Jurupa)

2 TP/RC TP/RC TR/RC HC/CP

Mira Loma (Van Buren) CP CP CP HC/CP CP

Mission Viejo RC TR/RC TR/RC EX/RC

Norco TR/RC

Ontario Fire Station HC EX/RC

Palm Springs TP/RC TP/RC TP TP/RC EX/TP

Pasadena TR/RC TR/HC TR/RC EX/RC

Perris TP TR

Pico Rivera #2 RC HC HC EX/RC EX

Pomona RC RC HC

Redlands TP/RC TP/RC

Rehrig (Exide) SO

Reseda RC TR/RC HC EX/RC

Riverside HC TR/RC EX/RC EX

Rubidoux TR/RC TR/RC TR TR/HC TR/HC EX/TR/HC EX

San Bernardino TR/RC TP/RC TR/HC TR/HC EX/TR EX

Santa Clarita RC TP/RC TP/HC RC EX/RC

South Long Beach HC EX/SO EX

Uddelholm (Trojan Battery) SO

Temecula1

Upland RC TR/RC TR/RC EX

Van Nuys Airport SO

West Los Angeles RC TR/HC RC

1

Site to begin in 2010

2

Site to be closed in 2010 or 2011
14

TABLE 4 Continuous PM10/PM2.5 Monitoring Purpose, Objective, and Spatial Scales

MONITORING OBJECTIVE SPATIAL SCALE TYPE

HC – High Concentrations MI – Microscale TEOM

RC – Representative Concentrations NS – Neighborhood Scale BAM (NON-FEM)

BAM (FEM)

MONITORING PURPOSE

SO – Source Impact RM – Real-Time Reporting/Modeling

TP – Pollutant Transport SPM – Special Purpose Monitoring

TR – Trend Analysis

Location Continuous PM10 Continuous PM2.5

Type Purpose Objective Scale Type Purpose Objective Scale

Anaheim 1 BAM RM RC NS BAM/FEM SPM RC NS

Banning Airport BAM/NON-FEM RM RC NS

Burbank 1 TEOM RM RC NS BAM/FEM SPM RC NS

Crestline BAM/NON-FEM RM RC NS

Glendora BAM RM RC NS BAM/NON-FEM RM RC NS

Indio TEOM RM HC NS

Lake Elsinore TEOM RM RC NS BAM/NON-FEM RM RC NS

Long Beach (North) 1 BAM RM RC NS BAM/FEM SPM RC NS

Los Angeles (Main St.) 1 BAM RM RC NS BAM/FEM SPM HC NS

Mira Loma (Jurupa) TEOM RM HC NS

Mira Loma (Van Buren) 1 BAM RM HC NS BAM/FEM SPM HC NS

Palm Springs TEOM RM HC NS

Reseda BAM/NON-FEM RM RC NS

Riverside BAM RM HC NS BAM/NON-FEM RM HC NS

Rubidoux 1 TEOM RM HC NS BAM/FEM & NONFEM SPM/RM HC NS

San Bernardino TEOM RM RC NS

Santa Clarita BAM/NON-FEM RM RC NS

South Long Beach 1 BAM/FEM SPM RC NS

Temecula 2 BAM/NON-FEM RM RC NS

Upland BAM RM RC NS BAM/NON-FEM RM RC NS

1

 PM2.5 FEM BAM Samplers replaced NON-FEM Samplers during FY 2008-2009 and designated as special purpose monitors

2

 Site planned during Fiscal Year 2010-2011
15

TABLE 5 PM2.5 FRM Monitoring Stations Assigned Site Numbers

Location Site Code CARB No. AQS No. Start Date Schedule

Anaheim ANAH 30178 060590007 01/03/99 Daily

Azusa AZUS 70060 060370002 01/04/99 1-in-3

Big Bear BGBR 36001 060718001 02/08/99 1-in-6

Burbank1

BURK 70069 060371002 01/21/99 Daily

Compton COMP 70112 060371302 11/08 1-in-3

Fontana FONT 36197 060712002 01/03/99 1-in-3

Indio “A” INDI 33157 060652002 01/30/99 1-in-3

Indio “B” INDI 33157 060652002 05/12/00 1-in-6

Long Beach (North) LGBH 70072 060374002 01/03/99 Daily

Los Angeles “A” (Main St.) CELA 70087 060371103 01/03/99 Daily

Los Angeles “B” (Main St.) CELA 70087 060371103 01/06/99 1-in-6

Mira Loma (Van Buren) MRLM 33165 060658005 11/09/05 Daily

Mission Viejo MSVJ 30002 060592022 06/15/99 1-in-3

Ontario Fire Station ONFS 36025 060710025 01/03/99 1-in-3

Palm Springs PLSP 33137 060655001 12/26/99 1-in-3

Pasadena PASA 70088 060372005 03/04/99 1-in-3

Pico Rivera #2 PICO 70185 060371602 09/12/05 1-in-3

Reseda RESE 70074 060371201 01/24/99 1-in-3

Riverside RIVM 33146 060651003 01/06/99 1-in-3

Rubidoux “A” RIVR 33144 060658001 01/03/99 Daily

Rubidoux “B” RIVR 33144 060658001 01/03/99 1-in-6

San Bernardino SNBO 36203 060719004 01/03/99 1-in-3

South Long Beach SLGB 70110 060374004 06/20/03 Daily

1 Changed to daily on 04/16/09 for comparison to FEM BAM
16

TABLE 6 PAMS Network

July 1 to September 30 October 1 to June 30

Site 

Type

Date 

Established as 

PAMS

Site / AQS ID# VOC Carbonyl VOC Carbonyl Additional 

Requirements

1 04/01/2004

LAX Hastings 

(replaced 

Hawthorne)

8 x 3 hr samples every 

3rd day and 1 x 24 hr 

sample every 6th day

No Sampling 1 x 24 hr sample 

every 6th day No Sampling

2 06/01/1995 Azusa

8 x 3 hr samples every 

3rd day and 1 x 24 hr 

sample every 6th day

No Sampling 1 x 24 hr sample 

every 6th day No Sampling No/NOx required

2 07/01/1997 Burbank

Continuous GC and 

1 x 24 hr sample every 

6th day

8 x 3 hr samples every 

day and 1 x 24 hr 

sample every 6th day

1 x 24 hr sample 

every 6th day

1 x 24 hr sample 

every 6th day

2 06/01/2009 Los Angeles (Main)

8 x 3 hr samples every 

3rd day and 1 x 24 hr 

sample every 6th day

8 x 3 hr samples every 

3rd day and 1 x 24 hr 

sample every 6th day

1 x 24 hr sample 

every 6th day

1 x 24 hr sample 

every 6th day

Trace level CO required 

at one type 2 site.

2 08/01/2005 Pico Rivera #2

Continuous GC and 

1 x 24 hr sample every 

6th day

8 x 3 hr samples every 

day and 1 x 24 hr 

sample every 6th day

1 x 24 hr sample 

every 6th day

1 x 24 hr sample 

every 6th day

3 06/09/2009 Rubidoux

8 x 3 hr samples every 

3rd day and 1 x 24 hr 

sample every 6th day

No Sampling 1 x 24 hr sample 

every 6th day No Sampling NOy required

3 05/01/2001 Santa Clarita

8 x 3 hr samples every 

3rd day and 1 x 24 hr 

sample every 6th day

8 x 3 hr samples every 

3rd day and 1 x 24 hr 

sample every 6th day

1 x 24 hr sample 

every 6th day

1 x 24 hr sample 

every 6th day

SITE TYPES: MONITORING REQUIREMENTS: REDUCED REQUIREMENTS:

1 – Upwind and background characterization site One type 1 or type 3 site required per area Speciated VOC only required at type 2 and one other 

(type 1 or 3)

2 – Maximum O3 precursor emissions impact site One type 2 site required per area Carbonyl only required in areas classified as serious 

or above 8 hr zone

3 – Maximum O3 concentration site No type 4 required NO/NOx required only at type 2

4 – Extreme downwind monitoring site NOy required at one site per PAMS area (type 1 or 3)
17

TABLE 7 Ambient Air Quality Standards
18 Highest concentration

Micro, middle, neighborhood 

(sometimes urban for secondary formed 

pollutants such as ozone)

Population oriented Neighborhood, urban

Source Impact Micro, middle, neighborhood

Background and regional transport Urban, regional

Welfare based Urban, regional

Monitoring Objective/Site Type and Scale of Representativeness

TABLE 8 Relationship Between Monitoring Objective/Site Type and Scale 

of Representativeness

MSA population Most recent 3 year design 

value > 85% of O3 NAAQS

Most recent 3 year design 

value < 85% of O3 

NAAQS1

> 10 million 4 2

4 - 10 million 3 1

350,000 - < 4 million 2 1

50,000 - 350,000 1 0

1

 - mimimum monitoring requirements apply in absence of a design value

TABLE 9 Minimum Ozone Monitoring Requirements

MSA population

Most recent 3 year design 

value > 85% of PM2.5 

NAAQS

Most recent 3 year design 

value < 85% of PM2.5 

NAAQS

> 1,000,000 3 2

500,000-

1,000,000

2 1

50,000-500,000 1 0

TABLE 10 Minimum PM10 Monitoring Requirements

Population

High 

Concentration1

Medium 

Concentration2

Low 

Concentration3

>1,000,000 6-10 4-8 2-4

500,000-1,000,000 4-8 2-4 1-2

250,000-500,000 3-4 1-2 0-1

100,000-250,000 1-2 0-1 0

1

 - High concentrations are those that exceed PM2.5 NAAQS by 20% or more

2

 - Medium concentrations are those where ambient concentrations > 80% NAAQS

3

 - Low concentrations ar those where ambient concentrations are < 80% NAAQS

TABLE 11 Minimum PM2.5 Monitoring Requirements
19

Measurement Spacing from obstructions Inlet probe height

All neighborhood scale 

criteria pollutants >1 m 2 - 15 m

Middle and micro scale 

particulate pollutants1 >2 m 2 - 7 m

Near roadway 

microscale CO > 1 m 3 +/- 1/2 m

1

 2 m apart for flow rates > 200 lpm and 1 m apart for flow rates < 200 lpm

TABLE 12 Horizontal and Vertical Inlet Probe Placement

Roadway Average 

DailyTraffic

O3 & NO2 at 

neighborhood and 

urban scale

< 1,000 10

10,000 20

15,000 30

20,000 40

40,000 60

70,000 100

> 110,000 250

TABLE 13 Minimum Seperation Between 

Nearest Traffic Lane and Probe Inlet

Roadway Average 

DailyTraffic

CO at neighborhood 

scale

< 10,000 10

15,000 25

20,000 45

30,000 80

40,000 115

50,000 135

> 60,000 150

TABLE 14 Minimum Separation Between 

Nearest Traffic Lane and Probe Inlet
20

FIGURE 1 Distance of PM Samplers to Nearest Traffic Lane in Meters

Source: CFR 40 § 58 Appendix E
21

II. SITE ASSESSMENTS

OVERVIEW

This section describes the process that was undertaken for assessing individual sites in the South 

Coast AQMD monitoring network. It describes criteria used to assess sites, which include site 

history, security of future occupancy, infrastructure, monitoring objectives, probe siting criteria, 

data uses, and cost. The assessment criteria also include potential synergies that are considered 

in assessing the importance of a monitoring site.

SITE ASSESSMENT CRITERIA DESCRIPTIONS

Site History/Longevity

Many sites in the South Coast AQMD network have been in operation for more than 20 

years. Establishing historical data trends over a period of time assists in determining the 

effectiveness of control measures. 

Security of Future Occupancy

Many of the sites in the South Coast AQMD network are established at properties that are 

leased on a monthly or annual basis. Many sites are located at municipal properties 

where continuance of the current agreement will not change in the foreseeable future. 

There are however, locations where property owner needs such as refusal to establish 

long term lease, expansion of facilities, remodeling, or increases in rent make security of 

future occupancy uncertain.

Infrastructure

Consideration of the infrastructure at air monitoring locations is a crucial part of the site 

assessment. The condition of the building, electrical capabilities, data communication 

capabilities, and space for expansion are evaluated.

Probe Criteria

The earliest monitoring stations were established in the late 1950’s and since that time 

urban development and changes in land use, population, and air quality trends have 

affected monitoring objectives and the probe siting criteria so that air pollution data may 

no longer adequately represent the intended area. Requirements for probe siting criteria

includes an examination of the horizontal and vertical probe placement, spacing of the 

probe from obstructions, spacing of the probe in relation to minor sources, and spacing of 

the probe from roadways based on the individual criteria pollutant spatial scale of 

representativeness and Average Daily Traffic (ADT).

Non-NAAQS Data Uses

Besides NAAQS compliance status evaluation and progress demonstrations, data from 

South Coast AQMD air monitoring stations is used for real-time public notification of air 

pollution events, air quality forecasting, and the analysis and modeling for strategic plan 

development, including the preparation of the Air Quality Management Plan (AQMP). 

Due to the large population in Southern California and the complexity of the geography 

and meteorology, a relatively large number of air monitoring stations are needed to 
22

adequately describe air quality and meteorology in South Coast AQMD’s jurisdiction. 

As a whole, the South Coast AQMD air monitoring network successfully meets the needs 

for planning, public notification, and forecasting purposes.

Public Notification

Data from the criteria pollutants that are measured continuously are available to 

the public in near real time, through the South Coast AQMD, U.S. EPA AirNow, 

and California Air Resourced Board websites, as well as through the South Coast 

AQMD Interactive Voice Response (IVR) automated phone system. Warnings of 

current air pollution events that occur are transmitted to the public via the South 

Coast AQMD website, fax, email, recorded phone messages, and press releases. 

The U.S. EPA EnviroFlash alert system is used to alert subscribers of measured 

unhealthy air quality by email, RSS feeds or Twitter alerts. At this time, air 

quality notifications are primarily driven by PM2.5 and summertime O3

measurements, although PM10 episodes can also occur occasionally during 

exceptional events (e.g., natural windblown dust events, wildfires, and fireworks 

displays). A robust real-time network is needed to support the accurate mapping 

of data and transmittal of episodic health information for the large population and 

geographic diversity of the SCAB and the Coachella Valley.

Air Quality Forecasting

South Coast AQMD provides daily air quality forecasts to the public, predicting 

day-in-advance concentrations and Air Quality Index (AQI) values of O3, PM2.5, 

PM10, CO, and NO2 for 38 source-receptor areas throughout South Coast 

AQMD’s jurisdiction. The forecasts are disseminated to the public through the 

South Coast AQMD and U.S. EPA AirNow websites, the South Coast AQMD

IVR phone system, and through the news media, as well as by subscription via 

fax, email, RSS feeds, and Twitter (using EnviroFlash). South Coast AQMD also 

provides high wind/windblown dust forecasts for the Coachella Valley for South 

Coast AQMD Rule 403.1, agricultural and wildland prescribed fire burn forecasts 

and, starting in November 2010, residential wood burning forecasts. South Coast 

AQMD air quality forecast tools utilize forecaster experience, empirical/statistical 

models, and prognostic grid models. Current and historical air quality and 

meteorological data are critical to the forecasting process. The South Coast 

AQMD measurements are used to develop the empirical models and to provide 

current inputs during daily forecast preparation. The monitoring data is also used 

to evaluate and refine the prognostic grid models.

Air Quality Planning

South Coast AQMD measurements are important for the air quality planning 

process, including strategic plan development to demonstrate future year 

attainment of the NAAQS. Current levels and historic air quality trends are 

documented as a component of the AQMP and reasonable further progress 

analysis. Meteorological and air quality models are used to simulate 

representative past episodes or longer periods, as compared to measured air 

quality data throughout the region. Emissions are then be adjusted in the model 
23

for future years based on projected population, business growth, infrastructure and

the effect of control measures to evaluate the efficacy of potential emissions 

control strategies. A relatively dense monitoring network of pollutants and their 

precursors is needed throughout the modeling domain to adequately evaluate the 

ability of the models to simulate air quality.

Health Studies

Support for air pollution research studies is prime objective in assessing the value 

of an air monitoring location. Air pollution data collected is used to supplement 

data collected by researchers working on health effects assessments. Sites used as 

platforms for scientific studies involved with health or welfare impacts, 

measurement methods development, or used as collaborative efforts with 

researchers are considered here due to their important role in supporting the air 

quality management program.

Environmental Justice (EJ)

Following the South Coast AQMD Board’s EJ initiatives in October 1997, the 

South Coast AQMD has been a leader in identifying and addressing community 

EJ concerns, particularly as raised by low income, ethnic minority communities 

who may be disproportionately impacted by localized emissions and mobile 

source pollutants. In support of the program, toxics monitoring and periodic 

health effects studies take place at air monitoring locations throughout the 

network. Support of these studies is taken into consideration while determining 

the value of an air monitoring location.

Cost

Assessment of the cost to relocate a site is an important factor is determining the value of 

a monitoring location. Cost assessment takes into account the availability of sampling 

locations in the area, as well as the cost of rent and the number of monitors at the 

sampling site.

Synergies

Consideration of potential synergies between monitoring programs and external 

objectives are taken into account while establishing the value of the monitoring location. 

Establishing synergies between monitoring programs such as NCore, PAMS, NATTS, 

Health Studies, and South Coast AQMD’s EJ programs enhance the value of the 

monitoring location. Synergies external to the air monitoring network that are taken into 

consideration while determining the value of the site include use of facilities by South 

Coast AQMD field inspection personnel for office space and data communications.

INDIVIDUAL SITE ASSESSMENTS

The current AQMD air monitoring network meets or exceeds U.S. EPA monitoring requirements 

and satisfies multiple monitoring purposes. Over the last twenty years, population, sources of 

pollution, ambient levels of pollution, and the surveillance air monitoring network have been 

modified such that the original monitoring objectives of each site may no longer apply. The 
24

effects of these factors, as well as data and monitoring needs, are assessed by site. 

Measurements taken at each air monitoring site, AQS number, and date of inception are shown 

in Table 1. The probe siting criteria assessment is shown in Table 15.

Anaheim

The Anaheim site was established at its current location at 1630 Pampas Lane in August 

2001 after moving from 1010 Harbor Blvd. due to sale of the Orange County Agricultural 

Department facility where the site had resided since 1981. We currently hold a 5 year

lease with the Anaheim School District for our current monitoring location and do not 

anticipate any changes in the near future. The infrastructure of the facility requires 

attention. The current monitoring platform began as a temporary location, and therefore 

was not supported adequately. The monitoring platform needs to be removed, and 

supported properly with a cement base. Concurrently, the compound in which the site is 

housed needs to be expanded and electrical wiring upgraded to accommodate the 

necessary changes to meet probe siting criteria. The site does not currently meet 40 CFR 

§ 58 Appendix E Probe Siting Criteria, specifically spacing from trees requirement and 

probe distance from traffic lane. Spacing from trees for all pollutants should be at least 

10 m and distance from traffic land should be a minimum of 10 m and 15 m respectively 

for gaseous and particulate pollutants. Distances are shown in Table 15. Non-NAAQS

data uses include modeling and forecasting of daily pollution levels for public 

information. Synergies between air monitoring programs include speciated PM2.5 

sampling, Radnet program, EJ, and regional toxics air monitoring studies. The cost to 

relocate the site to meet probe siting criteria is high due to the number of instruments at 

the site, cost of rent in the area, and length of service.

ATSF (Exide)

The ATSF site was established at its current location in January 1999 to monitor Pb 

source emissions from the Exide facility in the City of Commerce. We currently have an 

agreement with the owners of the property to allow air monitoring and do not anticipate 

any changes in the near future. The infrastructure is adequate and probe siting criteria 

meets requirements for source impact siting. The cost to move the location is low, 

however, the current site is the best available location.

Azusa

The Azusa site was established at its current location in January 1957. We currently hold 

a 5 year lease for our monitoring location and do not anticipate any changes in the near 

future. The infrastructure meets the needs of the air monitoring network. The site is in 

compliance with 40 CFR § 58 Appendix E Probe Siting Criteria. Non-NAAQS data uses 

include modeling and forecasting of daily pollution levels for public information. 

Synergies between air monitoring programs include PAMS, CARB, and administrative 

synergies include use of office space for Air Quality Inspectors. The cost to relocate the 

site is high due to the number of instruments at the site, cost of rent in the area, and 

length of service.
25

Banning Airport

The Banning Airport site was established at its current location during April 1997, after 

moving from the Banning-Alessandro air monitoring location. We hold a 4 year lease 

with the airport for our monitoring location and do not anticipate any changes in the near 

future. The infrastructure of the facility meets the needs of the air monitoring network. 

The site meets 40 CFR § 58 Appendix E Probe Siting Criteria. Non-NAAQS data uses 

include modeling and forecasting of daily pollution levels for public information. 

Administrative synergies include use of office space for Air Quality Inspectors. The cost 

to relocate the site to meet probe siting criteria is high due to the number of instruments 

at the site, cost of rent in the area, and length of service.

Big Bear

The Big Bear site was established at its current location in February 1999 to assess

PM2.5 winter wood smoke. We currently have a 2 year agreement with airport 

management and do not anticipate any changes in the near future. The infrastructure is 

adequate and meets 40 CFR § 58 Appendix E Probe Siting Criteria. The cost to move the 

location is low, and there have been no exceedances of the PM2.5 standard, however the 

cost to maintain the site is high due to the distant location. 

Burbank

The Burbank site was established at its current location at 228 West Palm Avenue during 

October 1961. We currently hold a 3 year lease with the owners of the monitoring 

location and do not anticipate any changes in the near future. The infrastructure of the 

facility is adequate. The site however does not currently meet 40 CFR § 58 Appendix E 

Probe Siting Criteria, specifically spacing from traffic lane for O3 and NO2 are 6.2 

meters short of requirement. Distances are shown in Table 15. Non-NAAQS data uses 

include modeling and forecasting of daily pollution levels for public information. 

Synergies between air monitoring programs include PAMS, BioWatch, Regional Toxics 

studies, and CARB Toxics monitoring. Administrative synergies include use of office 

space for Air Quality Inspectors. The cost to relocate the site to meet probe siting criteria

will be higher than the current location due to the high cost of rent in the area and number 

of monitors. 

Closet World (Quemetco)

The Closet World site was established at its current location in October 2008 to monitor 

Pb source emissions from the Quemetco facility in the City of Industry. We currently 

have an agreement with the owners of the property to allow us to sample and do not 

anticipate any changes in the near future. The infrastructure is adequate and probe siting 

criteria meets requirements for source impact siting. The cost to relocate is low due to a 

single instrument at the site.

Compton

The Compton site was established at its current location at 700 North Bullis Road in

January 2004 after moving from the Lynwood site due to inadequate site infrastructure. 

We currently hold a 10 year lease with the City of Compton for our current monitoring 

location and do not anticipate any changes in the near future. The infrastructure of the
26

site meets the needs of the air monitoring network. The site meets requirements of 40 

CFR § 58 Appendix E Probe Siting Criteria, spacing from roadways, trees, and 

obstructions. Non-NAAQS data uses include modeling and forecasting of daily pollution 

levels for public information. Administrative synergies include use of office space for 

Air Quality Inspectors. The cost to relocate the site is high due to the number of 

instruments at the site and cost of rent in the area.

Costa Mesa

The Costa Mesa site was established at its current location in November 1989. We 

currently hold a 5 year lease with the owners for our current monitoring location and do 

not anticipate any changes in the near future. The site lacks adequate space to expand to 

include particulate sampling. The site meets requirements of 40 CFR § 58 Appendix E 

Probe Siting Criteria, spacing from roadways, trees, and obstructions. Non-NAAQS data 

uses include modeling and forecasting of daily pollution levels for public information. 

Administrative synergies include use of office space for Air Quality Inspectors. The cost 

of relocating the site is significant; however, finding a site that can accommodate 

particulate sampling will add value to the network.

Crestline

The Crestline site was established at its current location at Lake Gregory in October

1973. We currently hold a month to month contract for our current monitoring location 

with the San Bernardino County Regional Parks Department, but do not anticipate any 

changes in the near future. The infrastructure of the facility requires attention. The 

current monitoring platform is outdated and lacks sufficient space. Money has been set 

aside for a new monitoring platform but basic infrastructure must be installed first. The 

site does not currently meet 40 CFR § 58 Appendix E Probe Siting Criteria, specifically 

spacing from trees requirement. Distances are shown in Table 15. Non-NAAQS data 

uses include modeling and forecasting of daily pollution levels for public information. 

The cost to relocate the site to meet probe siting criteria is high due to the number of 

instruments at the site, cost of rent, and length of service.

Fontana

The Fontana site was established at its current location at 14360 Arrow Highway during 

August 1981. We currently hold a month to month lease with San Bernardino County 

Fire for the monitoring location and do not anticipate any changes in the near future. The 

infrastructure meets the needs of the air monitoring network; however, there is no room 

for further expansion. The site is in compliance with 40 CFR § 58 Appendix E Probe 

Siting Criteria, however, the adjacent property is a large dirt lot which contains 

vegetation which will cause siting problems in the coming years. Non-NAAQS data uses 

include modeling and forecasting of daily pollution levels for public information. 

Synergies between air monitoring programs include speciated PM2.5 sampling, Radnet 

program, EJ, and Regional Toxics Air Monitoring Studies. The cost to relocate the site to 

meet probe siting criteria is high due to the number of instruments at the site, cost of rent 

in the area, and length of service.
27

Glendora

The Glendora site was established at its current location at 840 E. Laurel during August 

1980. We currently hold a month to month lease with the city of Glendora for our 

monitoring location and are concerned about the future stability of remaining at the 

location. The current monitoring platform is housed in a structure which requires 

attention. The site was established by California Air Resources Board in a now outdated 

housing. The monitoring platform needs to be removed, and supported properly with a 

cement base. Concurrently, the compound in which the site is housed needs to be 

expanded and electrical wiring upgraded to accommodate the necessary changes to meet 

probe siting criteria. The site is in compliance with 40 CFR § 58 Appendix E Probe 

Siting Criteria; however, the area is surrounded by a vacant dirt lot which can have an 

impact on particulate readings. Distances are shown in Table 15. Non-NAAQS data uses 

include modeling and forecasting of daily pollution levels for public information. 

Synergies between air monitoring programs include the BioWatch program, regional 

toxics studies, and regional health studies. The cost to relocate is high due to the number 

of instruments at the site, cost of rent in the area, and length of service. Cost can be 

mitigated by consolidating the site with nearby air monitoring locations.

Indio

The Indio site was established at its current location at 46-990 Jackson Street during 

January 1983. We currently hold a month to month lease with the city of Indio and do 

not anticipate any changes in the near future. The current monitoring platform is a 

modular wood structure, which requires extensive maintenance. Money has been set 

aside for a new monitoring platform. The site is in compliance with 40 CFR § 58 

Appendix E Probe Siting Criteria; however, the area is surrounded by a dirt lot 

occasionally used as parking which can have an impact on particulate readings. 

Distances are shown in Table 15. Non-NAAQS data uses include modeling and 

forecasting of daily pollution levels for public information. The cost to relocate the site 

to meet probe siting criteria is high due to the number of instruments at the site, cost of 

rent in the area, and length of service.

La Habra

The La Habra site was established at its current location at 621 West Lambert Road 

during August 1960. We currently hold a month to month lease with the city of La Habra 

and do not anticipate any changes in the near future. The site lacks adequate space to 

expand to include particulate sampling and the monitoring structure requires attention. 

The site does not currently meet 40 CFR § 58 Appendix E Probe Siting Criteria, 

specifically spacing from trees requirement and probe distance from traffic lane. Spacing 

from trees for all pollutants should be at least 10 m and distance from traffic land should 

be a minimum of 10 and 15 m respectively for gaseous and particulate pollutants. 

Distances are shown in Table 15. Non-NAAQS data uses include modeling and 

forecasting of daily pollution levels for public information. Synergies between air 

monitoring programs include speciated PM2.5 sampling, Radnet program, and regional 

toxics air monitoring studies. The cost to relocate the site to meet probe siting criteria is 

high due to the number of instruments at the site, cost of rent in the area, and length of 

service. Although the cost is significant, finding a site which can accommodate 
28

particulate sampling will add value to the network and costs can be mitigated by 

consolidation with an existing air monitoring location.

Lake Elsinore

The Lake Elsinore site was established at its current location at 506 West Flint St. during 

June 1987. We currently hold a 4 year lease with the City of Lake Elsinore for the 

monitoring location and do not anticipate any changes in the near future. The 

infrastructure meets the needs of the air monitoring network. The site is in compliance 

with 40 CFR § 58 Appendix E Probe Siting Criteria; however, the adjacent property 

contains vegetation which will cause siting problems in the coming years. Non-NAAQS 

data uses include modeling and forecasting of daily pollution levels for public 

information. Synergies between air monitoring programs include regional health studies. 

The cost to relocate the site to meet probe siting criteria is high due to the number of 

instruments at the site, cost of rent in the area, and length of service.

LAX Hastings

The LAX Hastings site was established at its current location at 7201 W. Westchester 

Parkway during April 2004. The site was established to replace the Hawthorne air

monitoring location located on the grounds of Anza Elementary School in Hawthorne, 

which was established to replace the Lennox air monitoring location. We currently hold 

a month to month lease with Los Angeles International Airport for the monitoring 

location and do not anticipate any changes in the near future. The infrastructure meets 

the needs of the air monitoring network; however, there is no room for further expansion

within the current compound. The site is in compliance with 40 CFR § 58 Appendix E 

Probe Siting Criteria. Non-NAAQS data uses include modeling and forecasting of daily 

pollution levels for public information. Synergies between air monitoring programs 

include PAMS and regional toxics air monitoring studies. The cost to relocate the site to 

meet probe siting criteria will be significant due to the number of samplers and the 

current low cost lease.

Long Beach (North)

The North Long Beach site was established at its current location at 3648 N Long Beach 

Blvd during October 1961. We currently hold a 4 year lease with the owners of the 

monitoring location and do not anticipate any changes in the near future. The 

infrastructure of the facility is adequate. The site however, does not currently meet 40 

CFR § 58 Appendix E Probe Siting Criteria, specifically spacing from traffic lane for O3, 

CO, NO2, PM10, and Pb. Distances are shown in Table 15. Non-NAAQS data uses 

include modeling and forecasting of daily pollution levels for public information. 

Synergies between air monitoring programs include Speciated PM2.5, Regional Health 

Studies, EJ, Regional Toxics studies, and CARB Toxics monitoring. Administrative 

synergies include use of office space for Air Quality Inspectors. The cost to relocate the 

site to meet probe siting criteria is high due to the number of instruments at the site, cost 

of rent in the area, and length of service.
29

Los Angeles (Main Street)

The Los Angeles Main Street site was established at its current location at 1630 North 

Main Street in September 1979. We currently hold a month to month lease with the Los 

Angeles Department of Water and Power (LADWP) for our current monitoring location 

and do not anticipate any changes in the near future. The infrastructure of the facility 

requires attention. The current monitoring platform lacks adequate space and power. 

Arrangements have been made with LADWP to update the space and power to meet the 

needs of the network during FY2010-11. The site is currently in compliance with 40 

CFR § 58 Appendix E Probe Siting Criteria. Non-NAAQS data uses include modeling 

and forecasting of daily pollution levels for public information. Synergies between air 

monitoring programs include speciated PM2.5 sampling, PAMS, STN, NATTS, NCORE,

EJ, regional health studies, regional toxics studies, and CARB Toxics monitoring. The 

cost to relocate the site is high due to the number of instruments at the site, cost of rent in 

the area, and length of service.

Mira Loma (Jurupa)

The Mira Loma Jurupa site was established at its current location at 10551 Bellegrave

during December 1993 by CARB as part of the Children’s Health Study. We currently 

have a no cost agreement with the Jurupa Unified School District for our monitoring 

location and are unsure about the future stability of remaining at the location. The 

current monitoring platform is housed in a structure which requires attention. The current 

monitoring platform began as a temporary location with no room for expansion and poor 

electrical infrastructure. The site does not meet 40 CFR § 58 Appendix E Probe Siting 

Criteria, specifically spacing from obstructions, which is detailed in Table 15. 

Non-NAAQS data uses include modeling and forecasting of daily pollution levels for 

public information. Synergies between air monitoring programs include regional health 

studies. The cost to relocate the site will be low due to a site established nearby to 

replace this site due to the poor infrastructure.

Mira Loma (Van Buren)

The Mira Loma Van Buren was established at its current location at 5130 Poinsettia 

Drive during November 2005. This location served as a replacement for the Mira Loma 

Jurupa site due to the location’s poor instrument siting and infrastructure. We currently 

have a no cost agreement with the Jurupa Unified School District for our monitoring 

location and do not anticipate any changes in the near future. The site is in compliance 

with the requirements of 40 CFR § 58 Appendix E Probe Criteria. Non-NAAQS data 

uses include modeling and forecasting of daily pollution levels for public information. 

Synergies between air monitoring programs include regional health studies and regional 

toxics studies. 

Mission Viejo

The Mission Viejo site was established at its current location at 26081 Via Pera during 

June 1999. We currently hold a 5 year lease with the El Toro Water District for the 

monitoring location and do not anticipate any changes in the near future. The 

infrastructure meets the needs of the air monitoring network; however, there is no room 

for further expansion within the current compound. The site is in compliance with 40 
30

CFR § 58 Appendix E Probe Siting Criteria. Non-NAAQS data uses include modeling 

and forecasting of daily pollution levels for public information. The cost to relocate the 

site to meet probe siting criteria will be significant due to the number of samplers and the 

current low cost lease.

Norco

The Norco site was established at its current location on the grounds of the Naval Surface 

Warfare Center in December 1980 to examine O3 and particulates. We currently have a 

5 year contract through 2014 and do not anticipate any changes in the near future. The 

infrastructure of the facility meets the needs of particulate sampling, but there are no 

facilities for continuous analyzers. The site is in compliance with 40 CFR § 58 Appendix 

E Probe Siting Criteria. The cost to maintain the site is high, with a technician traveling 

to the site to maintain a single instrument. Non-NAAQS data uses include modeling and 

forecasting of daily pollution levels for public information. There are no synergies 

between air monitoring programs or use of office space by inspectors. The cost to 

relocate the site is low to a single instrument at the site. This cost can be further

mitigated by consolidation with a nearby site.

Ontario Fire Station

The Ontario Fire Station site was established at its current location at 1408 E. Francis 

during January 1999. We currently hold a 4 year lease with the City of Ontario for our 

current monitoring location and do not anticipate any changes in the near future. The 

infrastructure of the facility meets the needs of particulate sampling, but there are no 

facilities for continuous analyzers. The site does not currently meet 40 CFR § 58 

Appendix E Probe Siting Criteria, specifically spacing from obstructions surrounding the 

instrumentation. Distances are shown in Table 15. Non-NAAQS data uses include 

modeling and forecasting of daily pollution levels for public information. There are no 

synergies between air monitoring programs or use of office space by inspectors. The cost 

to relocate the site is high due to the number of samplers but this can be mitigated by 

consolidation with a nearby site.

Palm Springs

The Palm Springs site was established at its current location at 590 Racquet Club Road

during April 1971. We currently hold a 4 year lease with the City of Palm Springs for 

our current monitoring location and do not anticipate any changes in the near future. The 

infrastructure of the facility currently meets the needs of the monitoring network, but 

there is no room for future expansion. The site does not currently meet 40 CFR § 58 

Appendix E Probe Siting Criteria, specifically spacing from obstructions and probe 

distance from traffic lane. Distances are shown in Table 15. Non-NAAQS data uses 

include modeling and forecasting of daily pollution levels for public information. There 

are no synergies between air monitoring programs or use of office space by inspectors. 

The cost to relocate the site to meet probe siting criteria will be high due to number of 

analyzers and length of service.
31

Pasadena

The Pasadena site was established at its current location at 752 Wilson Ave during April 

1982. We currently hold a month to month lease with the California Institute of 

Technology for our current monitoring location and do not anticipate any changes in the 

near future. The infrastructure of the facility requires attention. The current monitoring 

platform is housed in a structure, which is outdated. Money has been set aside for a new 

monitoring platform but basic infrastructure is lacking and the compound in which the 

site is housed needs to be expanded. The site does not currently meet 40 CFR § 58 

Appendix E Probe Siting Criteria, specifically spacing from trees requirement. Spacing 

from trees for all pollutants should be at least 10 m. Distances are shown in Table 15. 

Non-NAAQS data uses include modeling and forecasting of daily pollution levels for 

public information. There are no synergies between air monitoring programs or use of 

office space by inspectors. The cost to relocate the site to meet probe siting criteria will 

be higher due to the number of samplers, length of service, and cost of space in the area. 

Perris

The Perris site was established at its current location at 237 North D Street during May 

1973. We currently hold a 2 year lease for our current monitoring location with 

Riverside County and do not anticipate any changes in the near future. The current 

monitoring platform is housed in a structure which requires attention. The site does not 

currently meet 40 CFR § 58 Appendix E Probe Siting Criteria, specifically spacing from 

obstructions. Distances are shown in Table 15. Non-NAAQS data uses include 

modeling and forecasting of daily pollution levels for public information. There are no 

synergies between air monitoring programs or use of office space by inspectors. The cost 

to relocate the site to meet probe siting criteria will be higher than the current location, 

which is at no cost due to its location on a public facility.

Pico Rivera #2

The Pico Rivera #2 site was established at its current location at 4144 San Gabriel River 

Parkway in September 2005 after moving from 3713-B San Gabriel River Parkway due 

to influences from surrounding facilities. We currently hold a 2 year lease with the 

Whittier Utility Authority and do not anticipate any changes in the near future. The 

infrastructure of the facility meets the needs of the air monitoring network. The site is in 

compliance with 40 CFR § 58 Appendix E Probe Siting Criteria. Distances are shown in 

Table 15. Non-NAAQS data uses include modeling and forecasting of daily pollution 

levels for public information. Synergies between air monitoring programs include PAMS 

and Regional Toxics studies. The cost to relocate the site is high due to the number of 

samplers, length of service and cost of space in the area.

Pomona

The Pomona Fire Station site was established at its current location at 924 Garey Ave in 

June 1965 to investigate CO emissions from motor vehicles. We currently hold a 3 year 

lease and do not anticipate any changes in the near future. The infrastructure of the 

facility requires attention. The current monitoring building is outdated and does not 

allow for particulate sampling. The site does not currently meet 40 CFR § 58 Appendix 

E Probe Siting Criteria, specifically spacing from roadway for O3 and NO2. Distances 
32

are shown in Table 15. Non-NAAQS data uses include modeling and forecasting of daily 

pollution levels for public information. There are no synergies between air monitoring 

programs; however, calibration and repair technicians use space as a workshop. The cost 

to relocate the site is high due to the number of samplers and length of service, but this 

can be mitigated by consolidation with a nearby sites.

Redlands

The Redlands site was established at its current location at 500 Deerborn Ave during 

September 1986. We currently hold a month to month lease with the City of Redlands 

and do not anticipate any changes in the near future. The infrastructure of the facility 

requires attention. The current monitoring platform is housed in a structure which is 

outdated. Money has been set aside for a new monitoring platform, but basic 

infrastructure is lacking and the compound in which the site is housed needs to be 

expanded. The site does not currently meet 40 CFR § 58 Appendix E Probe Siting 

Criteria, specifically spacing from trees requirement. Spacing from trees for all 

pollutants should be at least 10 m. Distances are shown in Table 15. Non-NAAQS data 

uses include modeling and forecasting of daily pollution levels for public information. 

There are no synergies between air monitoring programs or use of office space. The cost 

to relocate the site to meet probe siting criteria will be higher than the current location 

which is on a public facility.

Rehrig (Exide)

The Rehrig site was established at 4010 E. 26th Street in the City of Vernon during 

October 2007 to monitor Pb source emissions from the Exide facility in the City of 

Vernon. We currently have an agreement with the owners of the property to allow us to 

sample and do not anticipate any changes in the near future. The infrastructure is 

adequate and probe siting criteria meets requirements for source impact siting. 

Reseda

The Reseda site was established at its current location at 18330 Gault Street during 

March 1965. We currently hold a 5 year lease with the owners of the monitoring location 

and do not anticipate any changes in the near future. The infrastructure of the facility is 

adequate. The site however does not currently meet 40 CFR § 58 Appendix E Probe

Siting Criteria, specifically spacing from traffic lane for O3 and NO2. Distances are 

shown in Table 15. Non-NAAQS data uses include modeling and forecasting of daily 

pollution levels for public information. There are no synergies between air monitoring 

programs; however, administrative synergies include use of office space for Air Quality 

Inspectors. The cost to relocate the site to meet probe siting criteria will be higher than 

the current location due to the high cost of rent in the area, number of monitors, and 

length of service.

Riverside (Magnolia)

The Riverside site was established at its current location at 7002 Magnolia Avenue 

during October 1972 by the CARB to investigate CO emissions from motor vehicles. We 

currently have a 3 year lease with the owners of the facility for our monitoring location 

and do not expect any changes in the near future. The monitoring platform meets the 
33

needs of the current monitoring program; however, there is no room for further 

expansion. The site does not meet 40 CFR § 58 Appendix E Probe Siting Criteria, 

specifically spacing from roadway which is detailed in Table 15. Non-NAAQS data uses 

include modeling and forecasting of daily pollution levels for public information. 

Synergies between air monitoring programs include health studies research; 

administrative synergies include use of office space for Air Quality Inspectors. The cost 

to relocate the site to meet probe siting criteria will be higher than the current location 

due to the high cost of rent in the area, number of monitors, and length of service.

Rubidoux

The Rubidoux site was established at its current location at 5888 Mission Boulevard 

during September 1972. We currently hold a 3 year lease with Southern California 

Edison for our current monitoring location and do not anticipate any changes in the near 

future. The infrastructure of the facility has been recently updated and meets the need of 

monitoring network. The site is currently in compliance with 40 CFR § 58 Appendix E 

Probe Siting Criteria. Non-NAAQS data uses include modeling and forecasting of daily 

pollution levels for public information. Synergies between air monitoring programs 

include speciated PM2.5 sampling, PAMS, STN, NATTS, NCORE, CARB Toxics 

monitoring, and regional toxics air monitoring studies. The cost to relocate the site to 

meet probe siting criteria will be higher than the current location due to the number of 

monitors, length of service, and cost of rent in the area.

San Bernardino

The San Bernardino site was established at its current location at 24302 East 4th Street 

during May 1986. We currently hold a 3 year lease with the City of San Bernardino 

Unified School District and do not anticipate any changes in the near future. The 

infrastructure of the facility requires attention. The current monitoring platform is 

housed in a structure which is outdated. Money has been set aside for a new monitoring 

platform, but basic infrastructure is lacking and the compound in which the site is housed 

needs to be expanded. The site is in compliance with 40 CFR § 58 Appendix E Probe

Siting Criteria with criteria shown in Table 15. Non-NAAQS data uses include modeling 

and forecasting of daily pollution levels for public information. Synergies between air 

monitoring programs include EJ and regional toxics studies. The cost to relocate the site 

to meet probe siting criteria will be higher than the current location due to the number of 

instruments, length of service, and cost of rent in the area. 

Santa Clarita

The Santa Clarita site was established at its current location at 22224 Placerita Canyon 

Road during May 2001 after moving from 24875 San Fernando Road at the request of 

Los Angeles County Fire Station #73. We currently have an agreement with Los Angeles 

County for space and do not anticipate any changes in the near future. The infrastructure 

of the facility meets the needs of the air monitoring network. The site is in compliance 

with 40 CFR § 58 Appendix E Probe Siting Criteria. Distances are shown in Table 15. 

Non-NAAQS data uses include modeling and forecasting of daily pollution levels for 

public information. Synergies between air monitoring programs include PAMS and 
34

Regional Toxics studies. The cost to relocate the site is high due to the number of 

samplers, length of service, and cost of space in the area. 

South Long Beach

The South Long Beach site was established at its current location at 1305 E Pacific Coast 

Highway during June 2003 to monitor particulate influence from port activities. We 

currently have an agreement to monitor with the Long Beach City College for our current 

monitoring location and do not anticipate any changes in the near future. The 

infrastructure of the facility meets the needs of particulate sampling, but there are no 

facilities for continuous analyzers and no room for expansion. The site does not currently 

meet 40 CFR § 58 Appendix E Probe Siting Criteria, specifically spacing from 

obstructions surrounding the instrumentation. Distances are shown in Table 15. NonNAAQS data uses include modeling and forecasting of daily pollution levels for public 

information. There are no synergies between air monitoring programs or use of office 

space by inspectors. The cost to relocate the site is low due to the number of samplers 

and this can be further mitigated by consolidation with a nearby site.

Temecula

The Temecula site was established at its current location at Lake Skinner MWD Facilities 

during July 2010. We currently hold an open ended lease with MWD for our current 

monitoring location and do not anticipate any changes in the near future. The 

infrastructure meets the needs of the monitoring network and is in compliance with 40 

CFR § 58 Appendix E Probe Siting Criteria. Non-NAAQS data uses include modeling 

and forecasting of daily pollution levels for public information. There are no synergies 

between air monitoring programs and the site is restricted to operations personnel only. 

Uddelholm

The Uddelholm site was established at 9313 Santa Fe Springs Road in the City of Santa 

Fe Springs during October 1992 to monitor Pb source emissions from the Trojan Battery

facility. We currently have an agreement with the owners of the property to allow us to 

sample and do not anticipate any changes in the near future. The infrastructure is 

adequate and probe siting criteria meets requirements for source impact siting.

Upland

The Upland site was established at its current location at 1350 San Bernardino Road 

during March 1973. We currently hold a month to month lease with the Upland Cascade 

Mobile Home Park for our monitoring location and do not anticipate any changes in the 

near future. The monitoring platform is adequate for the current location and the site is in 

compliance with 40 CFR § 58 Appendix E Probe Siting Criteria. Non-NAAQS data uses 

include modeling and forecasting of daily pollution levels for public information. 

Synergies between air monitoring programs include the regional health studies. The cost 

to relocate the site will be high due to potential higher rent, number of samplers, and 

length of service. This can be mitigated by consolidating the site with nearby air 

monitoring locations.
35

Van Nuys Airport

The Van Nuys Airport site was established at 16345 Raymer during January 2010 to 

monitor Pb source emissions from the Van Nuys Airport. We currently have an 

agreement with the owners of the property to allow us to sample and do not anticipate 

any changes in the near future. The infrastructure is adequate and probe siting criteria 

meets requirements for source impact siting.

West Los Angeles

The West Los Angeles site was established at its current location at Wilshire and 

Sawtelle Boulevards on the grounds of the Veterans Administration Hospital during May 

1984. We currently have an agreement with the VA Administration to monitor and do 

not anticipate any changes in the near future. The infrastructure of the facility requires 

attention. The current monitoring platform is housed in a structure which is outdated. 

The site is in compliance with 40 CFR § 58 Appendix E Probe Siting Criteria with 

criteria shown in Table 15. Non-NAAQS data uses include modeling and forecasting of 

daily pollution levels for public information. There are no synergies between air 

monitoring programs or use of office space. The cost to relocate the site to meet probe 

siting criteria will be higher than the current location due to the number of instruments, 

length of service, and cost of rent in the area.
36

1 Welding shop

2

Propeller airplane exhaust

TABLE 15 Probe Siting 

Metric

Horizontal 

and vertical 

placement

Spacing 

from 

minor 

sources

Spacing from 

obstructions

Spacing from trees Probe distance from 

traffic lane (m)

ADT 

Volume

Probe 

material and 

sample 

residence 

time

Station Pollutant Actual Required Actual Required

Anaheim O3 1 None None 6 >10 7.5 >10 <500 7.4

CO 1 None None 6 >10 7.5 >10 <500 6.4

NO2 1 None None 6 >10 7.5 >10 <500 7.5

PM10 2 None None 11 >10 10.5 >15 <500 NA

PM2.5 1 None None 8 >10 10 >15 <500 NA

Azusa O3 1 26 1 None 23 >10 14.5 >10 <500 7.9

CO 1 26 1None 23 >10 14.5 >10 <500 6.7

NO2 1 26 1None 23 >10 14.5 >10 <500 8.5

PM10 2 26 1None 23 >10 18.5 >15 <500 NA

PM2.5 1 26 1None 23 >10 15.8 >15 <500 NA

Banning O3 1 60 2

47 None 80 >20 <2000 8.2

NO2 1 60 247 None 80 >20 <2000 9.1

PM10 2 60 247 None 80 >15 <2000 NA

Big Bear PM2.5 1 None 32 36 >10 114 >15 2876 NA

Burbank O3 1 None None 18 >10 13.8 >20 <2000 6.5

CO 1 None None 18 >10 13.8 >10 <2000 6.3

NO2 1 None None 18 >10 13.8 >20 <2000 7.8

SO2 1 None None 18 >10 13.8 NA <2000 7.9

PM10 2 None None 19 >10 13.8 >15 <2000 NA

PM2.5 1 None None 20 >10 13.8 >15 <2000 NA

Compton O3 1 None None 16 >10 16.36 >10 <1000 7.6

CO 1 None None 16 >10 16.36 >10 <1000 8.7

NO2 1 None None 16 >10 16.36 >10 <1000 8.2

PM2.5 1 None None 13 >10 21 >15 <1000 NA

Pb 2 None None 17 >10 23 >15 <1000 NA

Costa 

Mesa

O3 1 None None 18 >10 34 >20 <2000 6.7

CO 1 None None 18 >10 34 >10 <2000 7.4

NO2 1 None None 18 >10 34 >20 <2000 8.8

SO2 1 None None 18 >10 34 NA <2000 9.5

Crestline O3 1 None None 9 >10 55 >20 <8000 10

PM10 2 None None 8 >10 55 >15 <8000 NA

PM2.5 2 None None 7 >10 55 >15 <8000 NA
37

TABLE 15 (cont) Probe Siting

Metric

Horizontal 

and vertical 

placement

Spacing from 

minor sources

Spacing from 

obstructions

Spacing from 

trees

Probe distance 

from traffic lane 

(m)

ADT 

Traffic 

Volume

Probe 

material and 

sample 

residence 

time

Station Pollutant Actual Required Actual Required

Fontana O3 1 9 3,4 None 19 >10 92 >30 12500 5.5

CO 1 9 3,4 None 19 >10 92 >25 12500 5.1

NO2 1 9 3,4 None 19 >10 92 >30 12500 6.0

SO2 1 9 3,4 None 19 >10 92 NA 12500 6.5

PM10 2 9 3,4 None 14 >10 86 >15 12500 NA

PM2.5 1 9 3,4 None 16 >10 86 >15 12500 NA

Glendora O3 1 None None 16 >10 121 >20 1834 7.6

CO 1 None None 16 >10 121 >10 1834 7.0

NO2 1 None None 16 >10 121 >20 1834 7.8

PM10 2 6 3 None 16 >10 121 >15 1834 NA

PM2.5 1 6 3None 16 >10 121 >15 1834 NA

Indio O3 1 6 3

60 None 88 >40 16528 12.5

PM10 2 6 360 None 88 >17 16528 NA

PM2.5 1 6 360 None 88 >17 16528 NA

La Habra O3 1 28 5 None 3 >10 40 >100 66200 7.5

CO 1 28 5 None 3 >10 40 >150 66200 6.1

NO2 1 28 5 None 3 >10 40 >100 66200 7.4

Lake 

Elsinore

O3 1 None None 17 >10 50 >20 <2000 5.1

CO 1 None None 17 >10 50 >10 <2000 5.1

NO2 1 None None 17 >10 50 >20 <2000 5.7

PM10 2 None None 10 >10 50 >15 <2000 NA

PM2.5 1 None None 10 >10 50 >15 <2000 NA

LAX 

Hastings

O3 1 600 6 None 20 >10 85 >20 <2000 6.1

CO 1 600 6 None 20 >10 85 >10 <2000 6.5

NO2 1 600 6 None 20 >10 85 >20 <2000 6.8

PM10 2 600 6 None 16 >10 92 >15 <2000 NA

Pb 2 600 6 None 16 >10 92 >15 <2000 NA

3

Unpaved parking

4

Diesel nearby

5

Refueling station nearby 

6

Airport runway nearby
38

7

Fire training facility

TABLE 15 (cont) Probe Siting

Metric

Horizontal 

and vertical 

placement

Spacing from 

minor sources

Spacing from 

obstructions Spacing from trees

Probe distance 

from traffic lane 

(m)

ADT 

Traffic 

Volume

Probe 

material and 

sample 

residence 

time

Station Pollutant Actual Required Actual Required

Long Beach 

(North)

O3 1 None 5 6 >10 8 >40 19900 6.9

CO (μs) 1 None 5 6 >10 8 2-10 19900 6.1

NO2 1 None 5 6 >10 8 >40 19900 8.4

SO2 1 None 5 6 >10 8 NA 19900 8.9

PM10 2 None 5 4 >10 8 >20 19900 NA

PM2.5 1 None 11 None 55 >20 19900 NA

Pb (μs) 2 None 5 4 >10 10 2-10 19900 NA

Los Angeles 

(Main St.)

O3 1 45 30 None 71 >40 15276 7.1

CO 1 45 30 None 71 >45 15276 7.2

NO2 1 45 30 None 71 >40 15276 7.6

SO2 1 45 30 None 71 NA 15276 9.5

PM10 2 27 52 None 51 >15 15276 NA

PM2.5 1 27 52 None 51 >15 15276 NA

Pb 2 27 52 None 51 >15 15276 NA

Mira Loma 

(Jurupa)

O3 1 None 2 None 165 >60 25717 4.5

CO 1 None 2 None 165 >80 25717 4.8

NO2 1 None 2 None 165 >60 25717 6.1

PM10 2 None 2 None 165 >25 25717 NA

Mira Loma 

(Van Buren)

O3 1 None None 36 >10 14 >10 <1000 6.7

CO 1 None None 36 >10 14 >10 <1000 5.9

NO2 1 None None 36 >10 14 >10 <1000 7.0

PM10 2 None None 40 >10 15 >15 <1000 NA

PM2.5 2 None None 40 >10 15 >15 <1000 NA

Mission 

Viejo

O3 1 None None None 138 >20 <2000 11.4

CO 1 None None None 138 >10 <2000 11.1

PM10 2 None None None 175 >15 <2000 NA

PM2.5 1 None None None 175 >15 <2000 NA

Norco PM10 2 None None 29 >10 25 >15 <500 NA

Ontario 

(FireStation)

PM10 2 96 77 18 >10 43 >15 <2000 NA

PM2.5 1 96 77 20 >10 43 >15 <2000 NA
39

3

Unpaved parking

8

Print shop

TABLE 15 (cont) Probe Siting

Metric

Horizontal 

and vertical 

placement

Spacing from 

minor sources

Spacing from 

obstructions Spacing from trees

Probe distance 

from traffic lane 

(m)

ADT 

Traffic 

Volume

Probe 

material and 

sample 

residence 

time

Station Pollutant Actual Required Actual Required

Palm 

Springs

O3 1 None None 22 >10 17 >20 <5000 9.3

CO 1 None None 22 >10 17 >10 <5000 8.3

NO2 1 None None 22 >10 17 >20 <5000 9.5

PM10 2 None 3 19 >10 20 >15 <5000 NA

PM2.5 1 None 3 19 >10 13 >15 <5000 NA

Pasadena O3 1 None None 6 >10 66 >20 <5000 6.7

CO 1 None None 6 >10 66 >10 <5000 6.1

NO2 1 None None 6 >10 66 >20 <5000 6.7

PM2.5 1 None None 6 >10 70 >15 <5000 NA

Perris O3 1 None 7 30 >10 74 >60 39500 7.4

PM 10 2 None 7 30 >10 74 >40 39500 NA

Pico Rivera O3 1 9 3 None 30 >10 41 >40 <20000 6.8

CO 1 9 3 None 30 >10 41 >45 <20000 6.7

NO2 1 4 3 None 30 >10 41 >40 <20000 6.5

PM2.5 1 4 3 None 27 >10 35 >20 <20000 NA

Pb/SO4 2 4 3 None 27 >10 35 >20 <20000 NA

Pomona O3 1 None None None 7 >60 25000 7.4

CO (μs) 1 None None None 7 2-10 25000 7.0

NO2 1 None None None 7 >60 25000 8.2

Redlands O3 1 2 3 None 8 >10 26 >20 4709 17.5

PM10 2 2 3 None 10 >10 26 >15 4709 NA

Reseda O3 1 10 10 None 14 >10 16 >20 <2000 6.7

CO 1 10 10 None 14 >10 16 >10 <2000 6.0

NO2 1 10 10 None 14 >10 16 >20 <2000 7.8

PM2.5 1 10 10 None 14 >10 19 >15 <2000 NA

Riverside CO (μs) 1 None None 15 >10 27 2-10 40,000 11.4

NO2 1 None None 15 >10 27 >60 40,000 12.9

PM2.5 1 None None 15 >10 28 >40 40,000 NA

Pb/SO4(μs) 2 None None 15 >10 28 2-10 40,000 NA
40

TABLE 15 (cont) Probe Siting

Metric

Horizontal 

and vertical 

placement

Spacing from 

minor sources

Spacing from 

obstructions

Spacing from 

trees (m)

Probe distance 

from traffic lane 

(m)

ADT 

Traffic 

Volume

Probe material 

and sample 

residence time

Station Pollutant Actual Required Actual Required

Rubidoux O3 1 None 38 10 >10 119 >40 <20,000 4.7

CO 1 None 38 10 >10 119 >45 <20,000 5.6

NO2 1 None 38 10 >10 119 >40 <20,000 7.6

SO2 1 None 38 10 >10 119 NA <20,000 7.5

PM10 2 None 18 10 >10 119 >20 <20,000 NA

PM2.5 1 None 20 10 >10 119 >20 <20,000 NA

Pb/SO4 2 None 18 10 >10 119 >20 <20,000 NA

San 

Bernardino

O3 1 None None 14 >10 23 >20 <2500 7.9

CO 1 None None 14 >10 23 >10 <2500 7.4

NO2 1 None None 14 >10 23 >20 <2500 8.7

PM10 2 None None 19 >10 16 >15 <2500 NA

PM2.5 1 None None 19 >10 16 >15 <2500 NA

Pb 2 None None 19 >10 16 >15 <2500 NA

Santa Clarita O3 1 None None 30 >10 91 >20 <5000 6.6

CO 1 None None 30 >10 91 >10 <5000 6.0

NO2 1 None None 30 >10 91 >20 <5000 6.5

PM10 2 None None 30 >10 91 >15 <5000 NA

PM2.5 1 None None 30 >10 91 >15 <5000 NA

Long Beach 

(South)

PM10 2 None 20 None 86 >15 <10000 NA

PM2.5 1 None 20 None 86 >15 <10000 NA

Pb/SO4 2 None 20 None 86 >15 <10000 NA

Temecula O3 1 450 10

30 960 >10 1056 >20 6500 TBD

PM10 2 450 10 30 960 >10 1056 >15 6500 TBD

Upland O3 1 None None 19 >10 80 >20 <10000 9.5

CO 1 None None 19 >10 80 >10 <10000 8.4

NO2 1 None None 19 >10 80 >20 <10000 8.7

PM10 2 None None 12 >10 80 >15 <10000 NA

PM2.5 1 None None 12 >10 80 >15 <10000 NA

Pb/SO4 2 None None 12 >10 80 >15 <10000 NA

West Los 

Angeles

O3 1 None None 45 >10 23 >20 <10000 7.5

CO 1 None None 45 >10 23 >10 <10000 6.9

NO2 1 None None 45 >10 23 >20 <10000 7.9

9 Microwave tower

10 Water treatment facility
41

Building Electricity Communications Space Obstructions Distance from 

Traffic Lane

Anaheim 9 Secure Inadequate Inadequate Adequate Inadequate Obstructed Inadequate Yes High No

ATSF 10 Secure Adequate Adequate Adequate Adequate Unobstructed Adequate No Low No

Azusa 53 Secure Adequate Adequate Adequate Adequate Unobstructed Adequate Yes Low Yes

Banning Airport 13 Secure Adequate Adequate Adequate Adequate Unobstructed Adequate Yes High Yes

Big Bear 11 Secure Adequate Adequate Adequate Adequate Unobstructed Adequate No Low No

Burbank 49 Secure Adequate Adequate Adequate Adequate Unobstructed Inadequate Yes High Yes

Closet World 2 Secure NA Adequate NA Adequate Unobstructed Adequate No Low No

Compton 6 Secure Adequate Adequate Adequate Adequate Unobstructed Adequate Yes High Yes

Costa Mesa 21 Secure No No Adequate No Unobstructed Adequate Yes High Yes

Crestline 37 Secure No No Adequate Adequate Unobstructed Adequate Yes High No

Fontana 29 Secure Adequate Adequate Adequate No Obstructed Adequate Yes High Yes

Glendora 30 No No Adequate Adequate No Unobstructed Adequate Yes Low Yes

Indio 27 Secure No Adequate Adequate No Obstructed Adequate Yes High No

La Habra 50 Secure No No No No Obstructed Inadequate No High No

Lake Elsinore 23 Secure Adequate Adequate Adequate Adequate Unobstructed Adequate Yes High Yes

LAX Hastings 6 Secure Adequate Adequate Adequate No Unobstructed Adequate Yes High Yes

Long Beach (North) 48 Secure Adequate Adequate Adequate Adequate Obstructed Inadequate Yes High Yes

Los Angeles (Main 

Street) 31 Secure No No No No Unobstructed Adequate Yes High Yes

Mira Loma (Jurupa) 17 No No No No No Obstructed Adequate Yes Low Yes

Mira Loma (Van 

Buren) 5 Secure Adequate Adequate Adequate Adequate Unobstructed Adequate Yes High Yes

Mission Viejo 11 Secure Adequate Adequate Adequate No Unobstructed Adequate No High No

TABLE 16 Individual Site Assessment Summary

Cost to 

Move

Synergies 

Gained

Security of 

Future 

Occupancy

Site Longevity 

(Years)

Infrastructure Probe and Monitoring Path 

Criteria Data Use 

Other Than 

NAAQS
42

Building Electricity Communications Space obstructed Distance from 

Traffic Lane

Norco 30 Secure NA Adequate NA Inadequate Unobstructed Adequate No Low No

Ontario Fire 

Station

11 Secure NA Adequate NA Inadequate Unobstructed Adequate No High No

Palm Springs 39 Secure Adequate Adequate Adequate Inadequate Obstructed Inadequate No High No

Pasadena 28 Secure Inadequate Adequate Adequate Inadequate Obstructed Adequate No High No

Perris 37 Secure Inadequate Adequate Adequate Inadequate Obstructed Adequate No High No

Pico Rivera #2 5 Secure Adequate Adequate Adequate Adequate Unobstructed Adequate Yes High Yes

Pomona 45 Secure Inadequate Adequate Adequate Inadequate Unobstructed Inadequate No High No

Redlands 24 Secure Inadequate Adequate Adequate Adequate obstructed Adequate No High No

Rehrig (Exide) 3 Secure NA Adequate NA Adequate Unobstructed Adequate No Low No

Reseda 45 Secure Adequate Adequate Adequate Adequate Unobstructed Inadequate No High No

Riverside 

(Magnolia)

38 Secure Adequate Adequate Adequate Inadequate Obstructed Inadequate Yes High Yes

Rubidoux 38 Secure Adequate Adequate Adequate Adequate Unobstructed Adequate Yes High Yes

San Bernardino 24 Secure Inadequate Adequate Adequate Inadequate Unobstructed Adequate Yes High Yes

Santa Clarita 9 Secure Adequate Adequate Adequate Adequate Unobstructed Adequate Yes High Yes

South Long Beach 7 Secure NA Adequate NA Inadequate Obstructed Adequate Yes High No

Temecula < 1 yr Secure Adequate Adequate Adequate Adequate Unobstructed Adequate No High No

Uddelholm 

(Trojan Battery)

18 Secure NA Adequate Adequate Adequate Unobstructed Adequate No Low No

Upland 37 Secure Inadequate Adequate Adequate Adequate Unobstructed Adequate Yes High Yes

Van Nuys Airport < 1 yr Secure NA Adequate Adequate Adequate Unobstructed Adequate No Low No

West Los Angeles 26 Secure Inadequate Adequate NA Adequate Unobstructed Adequate Yes High No

TABLE 16 (cont) Individual Site Assessment Summary

Cost to 

Move

Synergies 

Gained Site Longevity

Security of 

Future 

Occupancy

Infrastructure Probe and Monitoring Path 

Criteria Data Use 

Other Than 

NAAQS
43

Site Issue Description

Spacing from trees - proximity to tree 

s/b > 10 m from dripline Anaheim is 6 m from palm tree.

Probe distance from traffic lane O3 CO and NO2 are 7.5 m s/b > 10 m; PM10 and PM2.5 are 10 

m s/b > 15 m for neighborhood scale

Azusa Spacing from minor sources Azusa is 26 m down wind from welding shop.

Banning Spacing from minor sources Banning is 60 m from leaded gasoline aircraft runway.

Burbank Probe distance from traffic lane O3 and NO2 are 13.8 m s/b > 20 m; PM10 and PM2.5 are 13.8 

m s/b > 15 m

Crestline Spacing from trees - proximity to tree 

s/b > 10 m from dripline Crestline is 8 m from pine tree.

Fontana

Spacing from minor sources

Fontana is 9 m from regularly idling diesel exhaust and unpaved 

parking. Particulate monitoring should not be located in 

unpaved areas.

Glendora Spacing from minor sources Glendora is 3 m from unpaved parking. Particulate monitoring 

should not be located in unpaved areas.

Indio Spacing from minor sources Indio is 3 m from unpaved parking. Particulate monitoring 

should not be located in unpaved areas.

Spacing from minor sources La Habra is 28 m from refueling facility.

Spacing from trees - proximity to tree 

s/b > 10 m from dripline La Habra is 3 m from cypress.

Probe distance from traffic lane O3 and NO2 are 40 m s/b > 100 m; CO is 40 m s/b > 150 m for 

neighborhood scale

Long Beach Probe distance from traffic lane O3 and NO2 are 8 m s/b > 40 m; PM10 is 8 m s/b > 20 m for 

neighborhood scale. Pb and CO are microscale

Spacing from obstructions North Long Beach is 5 m from building that exceeds height 

requirement for particulates.

Spacing from trees - proximity to tree 

s/b > 10 m from dripline North Long Beach is 4 m from tree.

Los Angeles (Main) Probe siting - inlet probe height Los Angeles (Main) inlet probe height > 2-15 m for 

neighborhood scale requirement

Mira Loma Spacing from obstructions Mira Loma (Jurupa) is 2 m from building which exceeds height 

requirement for particulates.

Spacing from obstructions Palm Springs is 3 m from building that exceeds height 

requirement for particulates.

Probe distance from traffic lane O3 and NO2 are 17 m s/b > 20 m

Pasadena Spacing from trees - proximity to tree 

s/b > 10 m from dripline Pasadena is 6 m from tree.

Spacing from minor sources Pico Rivera is 4 m from unpaved parking. Particulate 

monitoring should not be located in unpaved areas.

Probe distance from traffic lane CO is 41 m s/b > 45 m

Pomona Probe distance from traffic lane O3 and NO2 are 7 m s/b > 60 m; CO is microscale

Spacing from minor sources Redlands is 2 m from unpaved parking. Particulate monitoring 

should not be located in unpaved areas.

Spacing from trees - proximity to tree 

s/b > 10 m from dripline Redlands is 8 m from tree.

Spacing from minor sources Reseda is 10 m from print shop.

Probe distance from traffic lane O3 and NO2 are 16 m s/b > 20 m

Probe siting - inlet probe height Riverside roadside microscale CO > 3 +/- 1/2 m requirement

Probe distance from traffic lane NO2 is 27 m s/b > 60 m; particulate are 28 m s/b > 42 m except 

Pb (microscale)

TABLE 17 Summary Table

Palm Springs

Pico Rivera

Redlands

Reseda

Riverside

Anaheim

La Habra

Long Beach (North)
44

III. NETWORK ASSESSMENT

OVERVIEW

The current AQMD pollutant monitoring networks meet or exceed U.S. EPA monitoring 

requirements and satisfy multiple monitoring purposes. This section describes the process for 

assessing individual pollutant networks and monitoring programs in the South Coast AQMD

monitoring network. The criteria for assessing the networks include the examination of overall 

network monitoring objectives, the spatial scales of representativeness, the minimum number of 

monitors required by regulation, and correlation analysis to determine redundancy or gaps within 

each network.

NETWORK ASSESSMENT CRITERIA DESCRIPTIONS

The criteria used for network assessment are described below. They include an assessment of 

monitoring objectives and spatial scales relative to 40 CFR § 58 Appendix D criteria. Another 

criteria was a correlation analysis using the provided U.S. EPA tools to identify redundant sites 

or geographical areas which may need additional sites within a monitoring network. Finally, 

networks were evaluated against the regulatory requirements for the minimum number of 

monitors using the latest census data available.

Monitoring Objectives

Over the last twenty years, population, sources of pollution, ambient levels of pollution, 

and the South Coast AQMD air monitoring network have been modified. A periodic 

reassessment of monitoring objectives will help ensure that the current network design 

meets the original and any new monitoring objectives. 

Ambient air monitoring network design is specified, at a minimum, by the U.S. EPA and 

includes monitoring objectives and general criteria as outlined in 40 CFR § 58 Appendix 

D. Each pollutant measured at each air monitoring site is related to a specific monitoring 

objective. Depending on pollutant, air monitoring networks are designed to meet all or a 

subset of the following objectives:

 Highest concentrations expected to occur in the geographical area covered by the 

network. 

 Representative concentrations in areas of high population density in the 

geographical area covered by the network. 

 Impact of significant sources or source categories of pollution such as refineries 

or specific area sources such as residential fuel combustion. 

 Background concentration levels, usually located upwind of the air monitoring 

network. 

 Regional transport of pollution to areas outside of the monitoring network usually 

located downwind of the air monitoring network. 

 The last type of site required measures air pollution impacts on visibility, 

vegetation damage, or other welfare based impacts. 
45

Spatial Scale of Representativeness

Each monitoring objective or site type is also related to a specific spatial scale of 

representativeness as shown in Table 8. The goal in deciding on a location for a monitor 

is to correctly match the spatial scale of representativeness with the monitoring objective 

for the site being established. Spatial scale of representativeness is the physical 

dimension of the air parcel being represented by the air monitoring location. Spatial 

scales are defined as: 

 Microscale – represents concentrations in an area ranging from several meters to 

100 m.

 Middle scale – represents concentrations in an area from 100 m to .5 kilometers.

 Neighborhood scale – represents concentrations in an area that has uniform land 

use and is .5 kilometers to 4.0 kilometers.

 Urban scale – represents concentrations in an area the size of a city, from 4 to 50 

kilometers in size. Influence from sources of pollution may prevent homogenous 

representation of a pollutant on an urban scale.

 Regional scale – represents concentrations in a homogenous geographical area 

without large sources of pollution, usually tens to hundreds of kilometers in size.

Correlation Analysis

The U.S. EPA provided tools to assist in the network assessment process. The 

Correlation Matrix Analysis shows the correlation, relative difference, and distance 

between pairs of sites within a Core Based Statistical Area (CBSA) or a region. During 

the static analysis, each CBSA displays a graphical matrix for O3, PM2.5 reference, and 

equivalent methods and continuous particulate sites. The shape of ellipses represents the 

Pearson squared correlation between sites with circles representing zero correlation and a 

straight diagonal line representing a perfect correlation. The correlation between two 

sites quantitatively describes the degree of relatedness between the measurements made 

at two sites. The correlation, however, may indicate whether a pair of sites is related, but 

it does not indicate if one site consistently measures pollutant concentrations at levels 

substantially higher or lower than the other. For this purpose, the color of the ellipses 

represents the average relative difference between sites where the daily relative 

difference is defined as:

( 1, 2)

( 1 2)

avg s s

abs s  s

Where s1 and s2 represent the concentrations at sites one and two in the pairing, abs is 

the absolute difference between the two sites and avg is the average of the two site 

concentrations. The average relative difference between the two sites is an indicator of 

the overall measurement similarity between the two sites. Site pairs with a lower average 

relative difference are more similar to each other than pairs with a larger difference. The 

distance between the sites influences both the correlation and the relative difference 

between sites. Usually sites with a larger distance between them will generally be more 

poorly correlated and have large differences in the corresponding pollutant 
46

concentrations. The distance between site pairs in the correlation matrix graphic is 

displayed in kilometers in the middle of each ellipse. 

The purpose of this analysis tool is to provide a means of identifying potential redundant 

sites that could be removed. Potentially redundant sites exhibit fairly high correlations of 

0.8 consistently across all of their pairings and have low average relative difference, 

despite the distance between it and other sites. Usually, it is expected that correlation 

between sites will decrease as distance increases. However, for a regional air pollutant 

such as O3, sites in the same air shed can have very similar concentrations and be highly 

correlated. More unique sites will tend to exhibit the opposite characteristics. They will 

not be very well correlated with other sites and their relative difference would be higher 

than other site-to-site pairs.

Note that results from such a correlation analysis are just one criteria in assessing the 

value of sites within a network. Other site-specific or network design factors, such as 

health studies, EJ, inter-program synergies, long-term trends, and logistical constraints 

may add value to a site even if the measured concentrations are similar to other nearby 

sites. 

Minimum number of monitors

As a general requirement, the U.S. EPA specifies the minimum numbers of sites required 

in a criteria pollutant network based on the latest census population data. For instance, 

the minimum number of O3 sites required is based upon the MSA population and the 

most recent 3-year design value as shown in Table 9. These are minimum requirements 

and the total number of sites necessary to adequately satisfy all monitoring objectives 

may be higher. As of 2009, there were no minimum requirements for the number of CO, 

NO2, and SO2 monitoring sites in an air monitoring network. More recent minimum 

requirements for NO2 and SO2 are not considered in this assessment. Discontinuing 

operations within existing monitoring networks, even if not required by regulation, is 

usually subject to U.S. EPA Regional Administrator approval. One minimum 

requirement for the number of Pb sites is based upon estimated source emissions. A site 

must be located at maximum downwind concentration for each source that exceeds 1.0-

tons/year Pb emissions within the boundaries of the air monitoring network. Another 

minimum monitoring requirement for Pb is based on population. The number of PM10 

sites required is based upon MSA population data and design values as shown in Table 

10. The number of PM2.5 sites required is based upon MSA population data and 

measured concentrations as shown in Table 11. The final number of sites required may 

be more than the regulatory minimums dependent upon U.S. EPA Regional Approval of 

Annual Network Plans. 

The South Coast AQMD jurisdictional boundary encompasses two MSA’s as defined by 

the U.S. Office of Management and Budget and the U.S. Census Bureau. The Los 

Angeles-Long Beach-Santa Ana MSA (Code 31100) had a population of 12,365,627 

based on the year 2000 U.S. Census. The Riverside-San Bernardino-Ontario MSA (Code 

40140) had a population of 3,254,821 in 2000. The minimum number of monitors for 

each pollutant is based on MSA population and measured concentrations as described in 

40 CFR § 58 Appendix D. The South Coast AQMD network exceeds the minimum 

monitoring requirements for all criteria pollutants.
47

POLLUTANT NETWORK ASSESSMENTS

Ozone (O3)

O3 is formed when the precursor gases VOC and NOx react in the atmosphere with 

sunlight. Emissions from VOC and NOx sources are frequently trapped in the South 

Coast Basin by the surrounding mountains and a persistent inversion layer. This leads to 

high ozone values, especially during the summer and early fall months.

Regulatory Requirement

Local agencies must operate O3 monitoring sites at various locations depending 

upon population and O3 design values relative to the NAAQS. Ambient air 

quality standards for O3 have been set by both the State and Federal governments 

and continue to be made more stringent. The current ambient air quality 

standards for O3 are included in Table 7. To assess compliance with Federal and 

State standards, South Coast AQMD operates 30 sites with O3 measurements as 

part of the Air Monitoring Network. Figure 2 shows the spatial distribution of 

these sites.

Monitoring Objective

The majority of the O3 monitoring network sites have been designated as 

population exposure monitoring locations as depicted in Table 18. Sites 

downwind of the formation of O3 such as Santa Clarita, Crestline, Banning, 

Perris, Rubidoux, and San Bernardino areas tend to have much higher 

concentrations. The sites which recorded the highest 2008 O3 concentrations 

include: Central San Bernardino Mountains (Crestline), Central San Bernardino 

Valley 1 (Fontana), Santa Clarita, Central San Bernardino Valley 2 (San 

Bernardino), East San Gabriel Valley 2 (Glendora), North West San Bernardino 

Valley (Upland), East San Bernardino Valley (Redlands), and Banning. The 

preceding seven sites are representative of high concentration sites for O3. 

Background site designations are typically coastal areas. The following sites 

recorded the lowest O3 concentrations in 2008: South West Coastal LA County 

(LAX Hastings), Coastal LA County (North Long Beach), North Orange County 

(La Habra), Central Orange County (Anaheim), and South San Gabriel Valley 

(Pico Rivera 2). LAX Hastings and North Long Beach recorded the lowest 

concentrations and are more representative of background concentrations. As 

mentioned earlier, population trends show increasing development and population 

in the inland area. In general, the western sites in the O3 monitoring network 

provide lower value information than those inland sites to the north or east. The 

O3 monitoring network/population trend is depicted in Figure 3.
48

Spatial Scale of Representativeness

Monitoring objectives are matched with specific spatial scales of 

representativeness as shown in Table 18. When compared to the U.S. EPA 

criteria, some potential changes in monitoring objectives may be possible within 

the South Coast AQMD O3 network. The LAX Hastings and North Long Beach 

site record low concentrations of O3 and may be more consistent with background 

concentrations at the urban scale of representativeness. Other factors such as 

nearby roadways may also contribute to low O3 levels at North Long Beach. 

Station Monitoring objective Spatial Scale Site consistent with 

monitoring objective

Anaheim Population oriented Neighborhood Yes

Azusa High concentration Urban Yes

Banning Population oriented Neighborhood Yes

Burbank High concentration Urban Yes

Compton Population oriented Neighborhood Yes

Costa Mesa Population oriented Neighborhood Yes

Crestline High concentration Neighborhood Yes

Fontana Population oriented Urban Yes

Glendora High concentration Neighborhood Yes

Indio Population oriented Neighborhood Yes

La Habra Population oriented Neighborhood Yes

Lake Elsinore Population oriented Neighborhood Yes

LAX Hastings Population oriented Middle No

Long Beach (North) Population oriented Middle No

Los Angeles (Main St.) Population oriented Neighborhood Yes

Mira Loma (Jurupa) Population oriented Neighborhood Yes

Mira Loma (Van Buren) Population oriented Neighborhood Yes

Mission Viejo Population oriented Neighborhood Yes

Palm Springs Population oriented Neighborhood Yes

Pasadena Population oriented Neighborhood Yes

Perris Population oriented Neighborhood Yes

Pico Rivera High concentration Neighborhood Yes

Pomona High concentration Middle Yes

Redlands Population oriented Neighborhood Yes

Reseda High concentration Urban Yes

Rubidoux High concentration Urban Yes

San Bernardino High concentration Neighborhood Yes

Santa Clarita High concentration Urban Yes

Temecula TBD TBD TBD

Upland Population oriented Neighborhood Yes

West Los Angeles Population oriented Middle No

TABLE 18 O3 Network Design
49

Individual site assessments of the Spatial Scale of Representativeness for O3 are 

shown in Table 18.

Correlation Analysis

The correlation matrix analysis shows the correlation, relative difference, and 

distance between sites. The shape of the ellipses represents the Pearson Squared 

Correlation between sites with a circle representing zero correlation and a straight 

line representing perfect correlation; correlation between the sites represents the 

degree of relatedness. The correlation however, does not indicate if one site 

measures concentrations substantially higher or lower than another, for this the 

color of the ellipses represents the average relative difference. This analysis aids 

in determining sites that are redundant. Confounding factors affecting analysis 

include AQS site data with < 75% completion is not used. 

O3 correlation for 2008 between sites in Los Angeles, Orange, Riverside, and San 

Bernardino counties are shown in Figure 4. Site pairs that result in correlations 

greater than 0.8 and relative differences less than 0.3 for O3 are: 

60370002 (Azusa) with 060370016 (Glendora)

060371701 (Pomona)

060372005 (Pasadena)

060710004 (Upland)

060712002 (Fontana).

060370016 (Glendora) with 060371701 (Pomona)

060372005 (Pasadena)

060711004 (Upland)

060712004 (Fontana)

060371002 (Burbank) with 060371103 (Central LA)

060372005 (Pasadena).

060371103 (Central L.A.) with 060371602 (Pico Rivera 2)

060372005 (Pasadena).

060371701 (Pomona) with 060372005 (Pasadena)

060658001 (Rubidoux)

060711004 (Upland)

060712002 (Fontana)

060719004 (San Bernardino)

060590007 (Anaheim) with 060595001 (La Habra)

060650012 (Banning Airport) with 060651016 Torres Martinez (Indian 

Reservation not operated by South Coast 

AQMD)
50

060658001 (Rubidoux) with 060712002 (Fontana)

060714003 (Redlands)

060719004 (San Bernardino)

060711004 (Upland) with 060712002 (Fontana)

060712002 (Fontana) with 060714003 (Redlands)

060719004 (San Bernardino)

060714003 (Redlands) with 060719004 (San Bernardino).

This analysis shows that for O3, many sites generate comparable data. This result 

is expected for ozone given the regional nature of the pollutant and the density of 

the current network. Even if sites measure somewhat comparable ozone levels, 

the need for public reporting of health alert and AQI levels necessitates a 

relatively dense ozone network to capture spatial variability. Clusters of sites 

with generally highest correlations, small average differences, and close 

proximities include Fontana/Redlands/San_Bernardino/Rubidoux, 

Azusa/Glendora/Pomona/Upland/Fontana, and Anaheim/La Habra. 

O3 Minimum Monitoring Requirement

U.S. EPA criteria specify the minimum number of sites required in an air 

monitoring network based on MSA population and design value. Design values 

currently exceed the standard and population data was taken from the 2000 census 

to determine the required number of samplers for the SCAB and are shown in 

Table 19. The information shows that the South Coast AQMD air monitoring 

network significantly exceeds the required minimum numbers of samplers for O3.

Table 19 Minimum O3 Requirement

MSA Min. # 

Monitors 

Required

# 

Monitors 

Active

31100 4 17

40140 2 13

Carbon Monoxide

Carbon monoxide (CO) is a colorless, odorless gas that is formed when carbon in fuel is 

not burned completely. It is a component of motor vehicle exhaust, which contributes 

about 56 percent of all CO emissions nationwide. In cities, 85 to 95 percent of all CO 

emissions may come from motor vehicle exhaust. The highest levels of CO in ambient 

air typically occur during the colder months of the year when inversion conditions are 

more frequent. South Coast AQMD operates 26 sites with CO measurements as part of 

the South Coast AQMD air monitoring network. Figure 5 shows the spatial distribution 

of these sites.
51

Regulatory Requirement

Starting in the early 1970's, the EPA set national standards that have considerably 

reduced emissions of CO and other pollutants from motor vehicles. Since 1970, 

CO emissions from on-road vehicles have been reduced by over 40 percent. The 

greatest reductions have been in emissions from cars (nearly 60 percent). 

Currently, there is no minimum requirement for the number of CO monitoring 

sites. Continued operation of existing SLAMS, FRM, or FEMS is required until 

discontinuation is approved by the EPA Regional Administrator. Where SLAMS 

CO monitoring is ongoing, at least one site must be a maximum concentration site 

for the monitoring network.

Monitoring Objective

The CO monitoring network and population trends are depicted in Figure 6. The 

majority of the CO monitoring network sites are designated as population 

exposure sites. Review of the 2008 data indicates that Lynwood and Central 

Orange County (Anaheim) sites recorded the highest 8-hour average for CO in 

2008 as 4.3 ppm and 3.6 ppm respectively. The Lynwood air monitoring location 

was replaced in 2008 by the Compton location due to unstable infrastructure and 

after concurrent sampling showed that CO levels were comparable at the two 

sites. The lowest recorded values include the Palm Springs, Lake Elsinore, Santa 

Clarita, and Saddleback Valley (Mission Viejo) sites. The Compton site is 

consistent with high concentration levels of CO. The lowest levels are found at 

Palm Springs, Lake Elsinore, Santa Clarita, and Mission Viejo. All sites other 

than Compton and Anaheim are consistent with population exposure. The 

majority of sites remain on the west side where population growth has remained 

relatively stagnant. CO measurements in general are of lower value given the 

attainment status of the basin and the low design values. However, the prospect 

of new CO NAAQS adds value in terms of tracking long-term trends and spatial 

variability.
52

Spatial Scale of Representativeness

Most sites are consistent with the appropriate CO spatial scale of 

representativeness for the monitoring objective. Comparison of EPA criteria with 

Table 20 shows the LAX Hastings, Pasadena, Pomona, Rubidoux, and San 

Bernardino sites could be re-designated at different spatial scales that may be 

more consistent with monitoring objectives.

Correlation Analysis

Correlation analysis was not available for CO using EPA provided tools. This is 

due to the lack of a minimum number of required monitoring sites.

Minimum Number of Sites Required

For the CO monitoring network, there must only be one site designated as 

maximum concentration (Compton). All others may be considered for closure by 

Station Monitoring objective Spatial Scale Site consistent with 

monitoring objective

Anaheim High concentration Neighborhood Yes

Azusa Population oriented Neighborhood Yes

Burbank Population oriented Neighborhood Yes

Compton High concentration Middle Yes

Costa Mesa Population oriented Neighborhood Yes

Fontana Population oriented Neighborhood Yes

Glendora Population oriented Neighborhood Yes

La Habra Population oriented Neighborhood Yes

Lake Elsinore Population oriented Neighborhood Yes

LAX Hastings Population oriented Middle No

Long Beach (North) Population oriented Micro Yes

Los Angeles (Main St.) Population oriented Neighborhood Yes

Mira Loma (Jurupa) Population oriented Neighborhood Yes

Mira Loma (Van Buren) Population oriented Neighborhood Yes

Mission Viejo Population oriented Neighborhood Yes

Palm Springs Population oriented Neighborhood Yes

Pasadena Population oriented Middle No

Pico Rivera Population oriented Neighborhood Yes

Pomona Population oriented Micro No

Reseda Population oriented Neighborhood Yes

Riverside Population oriented Micro Yes

Rubidoux Population oriented Middle No

San Bernardino Population oriented Middle No

Santa Clarita Population oriented Neighborhood Yes

Upland Population oriented Neighborhood Yes

West Los Angeles Population oriented Neighborhood Yes

TABLE 20 CO Network Design
53

demonstrating either attainment has been reached and expected to be maintained, 

a monitor is consistently low relative to other monitors, a monitor has not 

measured a violation with NAAQS, a monitor has siting issues, a monitor is 

upwind of the urban area, or a site has logistical problems beyond agency control.

EPA criteria specify minimum numbers of sites required in an air monitoring 

network based on MSA population. Population data was taken from the 2000 

census to determine the required number of samplers for the SCAB and are shown 

in Table 21. The information shows that the South Coast AQMD air monitoring 

network significantly exceeds the required minimum numbers of samplers for 

CO.

Table 21 Minimum CO Requirement

MSA

Minimum Number 

of Monitors 

Required

Number of 

Monitors Active

31100 0 17

40140 0 9

Nitrogen Dioxide

Nitrogen dioxide (NO2) is one of a group of highly reactive gases known as "oxides of 

nitrogen," or "nitrogen oxides” (NOx). Some NO2 is emitted directly but most NO2 

forms in the atmosphere from the NO emissions from cars, trucks, buses, power plants, 

and any high-temperature combustion process. In addition to contributing to the 

formation of ground-level O3 and fine particle pollution, NO2 is linked with a number of 

adverse effects on the respiratory system. The South Coast AQMD operates 26 sites as 

part of the NO2 monitoring network. The spatial distribution of NO2 monitors is shown 

in Figure 7. Review of 1992 through 2009 data indicates that the annual NAAQS for 

NO2 was not exceeded.

Regulatory Requirement

As of 2009, there was no minimum requirement for the number of NO2 

monitoring sites. Continued operation of existing SLAMS sites is required until 

discontinuation is approved by the U.S. EPA Regional Administrator. Where 

SLAMS NO2 monitoring is ongoing, at least one site must be a maximum 

concentration site for the monitoring network. 

On February 9, 2010, EPA made revisions to the NO2 NAAQS requiring 

monitoring where maximum NO2 concentrations are expected to occur, including 

within 50 m of major roadways, as well as monitors sited to measure the areawide NO2 concentrations that occur more broadly across communities. To 

accomplish this, a two-tiered monitoring network is proposed for the NO2 

NAAQS. One tier (the near-road network) will reflect the much higher NO2 

concentrations that occur near-road and the second-tier (area-wide) characterizes 

the NO2 concentrations that occur in a larger area such as neighborhood or urban 
54

areas. However, these new NAAQS and monitoring regulations for NO2 are not 

considered in this assessment.

Monitoring Objective

There is no minimum requirement for the monitoring for NO2, but the U.S. EPA 

Regional Administrator must approve any reduction of the current operating 

monitoring network. The current NO2 monitoring network and population trends 

are shown in Figure 8. The majority of the NO2 monitoring network is 

designated as population exposure sites. A review of data indicates that the 

highest 1-hour concentrations in 2008 were recorded at the North Long Beach, 

Lynwood, and Central LA monitoring locations and the lowest concentrations 

were recorded at the Palm Springs and Lake Elsinore sites. During 2008, the 

Lynwood site was moved to the Compton location. The North Long Beach, 

Compton, and Central LA sites are more representative of high concentration sites 

than population exposure. The remainder of the sites are representative of 

population exposure. Monitors are distributed primarily in the western portion of 

the basin where higher NO2 levels are expected. Given the attainment status of 

the basin and the low ambient levels, these monitors are generally of lower value. 

However, the new 2010 NAAQS and monitoring requirements add value in terms 

of long-term trends and spatial variability.
55

Spatial Scale of Representativeness

Most sites were consistent with NO2 spatial scale of representativeness. 

Comparison of Table 22 with EPA criteria showed that the LAX Hastings, and 

Pomona sites could be designated at spatial scales that are more consistent with 

monitoring objectives. North Long Beach is more representative of a high 

concentration site at the neighborhood scale. The remainder of the sites are 

representative of population-oriented sites at the neighborhood scale.

Correlation Analysis

Correlation analysis was not available for NO2 using EPA provided tools. This is 

due to the lack of a minimum number of required monitoring sites.

Station Monitoring objective Spatial Scale Site consistent with 

monitoring objective

Anaheim Population oriented Urban Yes

Azusa Population oriented Urban Yes

Banning Population oriented Neighborhood Yes

Burbank Population oriented Neighborhood Yes

Compton High concentration Middle Yes

Costa Mesa Population oriented Neighborhood Yes

Fontana Population oriented Urban Yes

Glendora Population oriented Neighborhood Yes

La Habra Population oriented Urban Yes

Lake Elsinore Population oriented Neighborhood Yes

LAX Hastings Population oriented Middle No

Long Beach (North) High concentration Middle Yes

Los Angeles (Main St.) High concentration Neighborhood Yes

Mira Loma (Jurupa) Population oriented Neighborhood Yes

Mira Loma (Van Buren) Population oriented Neighborhood Yes

Palm Springs Population oriented Neighborhood Yes

Pasadena Population oriented Neighborhood Yes

Pico Rivera Population oriented Neighborhood Yes

Pomona Population oriented Middle No

Reseda Population oriented Urban Yes

Riverside Population oriented Urban Yes

Rubidoux Population oriented Urban Yes

San Bernardino Population oriented Urban Yes

Santa Clarita Population oriented Neighborhood Yes

Upland Population oriented Neighborhood Yes

West Los Angeles Population oriented Neighborhood Yes

TABLE 22 NO2 Network Design
56

Minimum Number of Sites Required

For the NO2 monitoring network, there must only be one site designated as 

maximum concentration. All others may be considered for closure by 

demonstrating either attainment has been reached and expected to be maintained, 

a monitor is consistently low relative to other monitors, a monitor has not 

measured a violation with NAAQS, a monitor has siting issues, a monitor is 

upwind of the urban area, or a site has logistical problems beyond agency control.

EPA criteria specify minimum numbers of sites required in an air monitoring 

network based on MSA population. Population data was taken from the 2000 

census to determine the required number of samplers for the SCAB and are shown 

in Table 23. The information shows that the South Coast AQMD air monitoring 

network significantly exceeds the required minimum numbers of samplers for 

NO2. Also included in the table is the new requirement for near roadway 

monitoring which is to begin operation by January 1, 2013.

Table 23 Minimum NO2 Requirement

MSA Minimum 

Number of 

Monitors 

Required

Number of 

Monitors 

Active

New Minimum 

Requirement

Near 

Roadway

Area Wide

31100 0 17 2 1

40140 0 9 2 1

Sulfur Dioxide

Sulfur dioxide (SO2) is one of a group of highly reactive gasses known as oxides of 

sulfur (SOx). The largest sources of SO2 emissions are from fossil fuel combustion at 

power plants and other industrial facilities. Smaller sources of SO2 emissions include 

industrial processes such as extracting metal from ore and the burning of high sulfur 

containing fuels by locomotives, large ships, and non-road equipment. South Coast 

AQMD operates SO2 monitors at 7 sites. Figure 9 shows the spatial distribution of the 

sites. The monitors are clustered mostly in the areas where SO2 sources may be located. 

The federal standard has not been exceeded in the basin for nearly 30 years.

Regulatory Requirement

The EPA first set standards for SO2 in 1971. The EPA set a twenty-four hour 

primary standard at 140 ppb and an annual average standard at 30 ppb (to protect 

health). The EPA also set a 3-hour average secondary standard at 500 ppb. 

Currently, there is no minimum requirement for the number of SO2 monitoring 

sites. Continued operation of existing SLAMS sites are required until 

discontinuation is approved by The U.S. EPA Regional Administrator. Where 

SLAMS SO2 monitoring is ongoing, at least one site must be designated a 

maximum concentration site. 

On June 2, 2010, the EPA strengthened the primary NAAQS for SO2. The EPA 

is also revising the ambient air monitoring requirements for SO2. States will need 
57

to make adjustments to the existing monitoring network in order to ensure that 

monitors meeting the new network design regulations are sited and operational by 

January 1, 2013. However, these new NAAQS and monitoring regulations for 

NO2 are not considered in this assessment.

The final monitoring regulations require monitors to be placed in Core Based 

Statistical Areas (CBSAs) based on a population weighted emissions index for the 

area. The final rule requires:

 3 monitors in CBSAs with index values of 1,000,000 or more;

 2 monitors in CBSAs with index values less than 1,000,000 but greater 

than 100,000; and

 1 monitor in CBSAs with index values greater than 5,000.

Monitoring Objective

As of 2009, there was no minimum requirement for the monitoring of SO2, but 

the U.S. EPA Regional Administrator must approve any reduction of the current 

monitoring network. The current SO2 monitoring network and population trends 

are shown in Figure 10. All SO2 monitors are designated as population oriented 

with the exception of North Long Beach, which is designated as high 

concentration as shown in Table 24. A review of the annual data shows that the 

maximum 1-hour concentration in 2008 was .09 ppm at North Long Beach and 

the next highest concentration was .02 ppm at LAX Hastings; the remaining sites 

were generally below the threshold for the monitoring instrumentation. The 

majority of the SO2 sites are in the western portion of the Basin. This is 

appropriate, even though the population growth has occurred inland, because the 

majority of SO2 sources are oil refineries located near the coast. North Long 

Beach should remain a high concentration site and the inland locations are 

appropriately designated as population oriented.

Spatial Scale of Representativeness

All SO2 spatial scales of representativeness were consistent with the monitoring 

objectives as shown in Table 24.

Station Monitoring objective Spatial Scale Site consistent with 

monitoring objective

Burbank Population oriented Neighborhood Yes

Costa Mesa Population oriented Neighborhood Yes

Fontana Population oriented Neighborhood Yes

LAX Hastings Population oriented Neighborhood Yes

Long Beach (North) High concentration Neighborhood Yes

Los Angeles (Main St.) Population oriented Neighborhood Yes

Rubidoux Population oriented Neighborhood Yes

TABLE 24 SO2 Network Design
58

Correlation Analysis

Correlation analysis was not available for SO2 using EPA provided tools. This is 

due to the lack of a minimum number of required sites. 

Minimum number of sites required

For the SO2 monitoring network, there must only be one site designated as 

maximum concentration. All others may be considered for closure by 

demonstrating either attainment has been reached and expected to be maintained, 

a monitor is consistently low relative to other monitors, a monitor has not 

measured a violation with NAAQS, a monitor has siting issues, a monitor is 

upwind of the urban area, or a site has logistical problems beyond agency control. 

EPA criteria specify the minimum number of sites required in an air monitoring 

network based on MSA population. Population data was taken from the 2000 

census to determine the required number of samplers for the SCAB and are shown 

in Table 25. The information shows that the South Coast AQMD air monitoring 

network significantly exceeds the required minimum numbers of samplers for 

CO. Also included in the table is the new requirement for monitoring which is to 

begin operation by January 1, 2013.

Table 25 Minimum SO2 Requirement

MSA Minimum 

Number of 

Monitors 

Required

Number of 

Monitors 

Active

New Minimum 

Requirement

Monitors 

Required

31100 0 5 2

40140 0 2 2

Pb

Pb is a metal found naturally in the environment as well as in manufactured products.

The major sources of Pb emissions have historically been motor vehicles (such as cars 

and trucks) and industrial sources. As a result of the EPA's regulatory efforts to remove 

Pb from gasoline, emissions of Pb from the transportation sector dramatically declined 

between 1980 and 1999, and levels of Pb in the air decreased by 94 percent between 1980 

and 1999. Today, the highest levels of Pb in air are usually found near Pb smelters. 

Other stationary sources are waste incinerators, utilities, and lead-acid battery 

manufacturers. Total Suspended Particulate (TSP) measurements are collected at 15 sites 

as part of the South Coast AQMD monitoring network; five of the sites are sourceoriented microscale Pb sites, and 10 sites measure population-oriented ambient Pb. The 

spatial distribution of these sites is shown in Figure 11.

Regulatory Requirement

On November 12, 2008, the EPA issued final revisions to the NAAQS standards 

for Pb. New network design requirements were implemented for monitoring 

sources of Pb (source-oriented monitoring) and urban Pb monitoring (non-source 

oriented). To meet this requirement, a new source-oriented site was established 

on January 1st, 2010 at the Van Nuys Airport and monitoring will continue at 
59

existing sites near the Exide (Vernon), Quemetco (City of Industry), and the 

Trojan Battery (Santa Fe Springs) facilities. 

Non source-oriented monitors are located in urban areas to gather information on 

general population Pb exposure. Starting January 1, 2011, one non sourceoriented monitor is required in each CBSA with a population > 500,000 as 

determined by the most recent census data. South Coast AQMD’s current Pb 

monitoring network exceeds the minimum required monitoring specified as part 

of the final revision to the NAAQS for Pb. 

Monitoring Objective

The current Pb monitoring network and population trends are shown in Figure 12. 

All of the non-source-oriented Pb monitoring network sites are populationoriented. The Pb monitoring network was put in place when leaded gasoline was 

still being used in automobiles. With the mainstream use of unleaded gasoline, 

concentrations of Pb have decreased with no clear high concentration site. 

Therefore, all of the non-source-oriented Pb monitoring have been re-designated 

as population-oriented monitoring locations. The source-oriented sites are 

appropriately considered source impact sites. 

Spatial Scale of Representativeness

The proper scale for the five source-oriented sites is microscale. The scale for the 

non-source-oriented sites are neighborhood scale or greater as shown in Table 26.

Station Monitoring objective Spatial Scale Site consistent with 

monitoring objective

ATSF (Exide-Vernon) Source impact Micro Yes

Closet World (QuemetcoCity of Industy)

Source impact Micro Yes

Compton Population oriented Neighborhood Yes

LAX Hastings Population oriented Neighborhood Yes

Long Beach (North) Population oriented Neighborhood Yes

Long Beach (South) Population oriented Neighborhood Yes

Los Angeles (Main St.) Population oriented Neighborhood Yes

Pico Rivera Population oriented Neighborhood Yes

Rehrig (Exide-Vernon) Source impact Micro Yes

Riverside Population oriented Neighborhood Yes

Rubidoux Population oriented Neighborhood Yes

San Bernardino Population oriented Neighborhood Yes

Uddelholm (Trojan 

Battery-Santa Fe Springs) Source impact Mico

Yes

Upland Population oriented Neighborhood Yes

Van Nuys Airport Source impact Micro Yes

TABLE 26 Pb Network Design
60

Correlation Analysis

Correlation analysis was not available for Pb using EPA provided tools. This was 

because most agencies across the country do not have an existing Pb monitoring 

network.

Minimum Number of Sites Required

EPA criteria specify the minimum number of sites required in an air monitoring 

network based on MSA population. Population data was taken from the 2000 

census to determine the required number of samplers for the SCAB and are shown 

in Table 27. Only two facilities exceed the 1.0 ton/year emissions threshold for 

source-oriented monitoring based on the latest data: Exide (Vernon) and Van 

Nuys Airport. The information shows that the South Coast AQMD air monitoring 

network significantly exceeds the required minimum numbers of samplers for Pb. 

Also included in the table is the new requirement for urban monitoring which is to 

begin operation by January 1, 2011.

Table 27 Minimum Pb Requirement

MSA Minimum Number of 

Monitors Required

Number of Monitors 

Active

New 

Minimum 

Requirement

Source 

Impact

Urban 

Monitoring

Source 

Impact

Urban 

Monitoring

Urban 

Monitoring

31100 2 0 5 6 1

40140 0 0 0 4 1

PM10

Particulate matter also known as particle pollution or PM, is a complex mixture of 

microscopic particles and liquid droplets. Particle pollution is made up of a number of 

components, including ions (such as nitrates and sulfates), organic chemicals, elemental 

carbon, metals, and soil or dust particles.

The size of particles is directly linked to their potential for causing health problems. The 

U.S. EPA regulates particles that are 10 micrometers (m) in diameter or less (PM10) 

because these particles generally pass through the throat and nose and enter the lungs. 

Once inhaled, these particles can affect the heart, lungs and cause serious health effects. 

"Inhalable coarse particles," are defined as larger than 2.5 m but smaller than 10 m in 

diameter. 

Regulatory Requirement

The nation's air quality standards for particulate matter were first established in 

1971 and were not significantly revised until 1987, when the EPA changed the 

indicator of the standards to regulate inhalable particles smaller than or equal to 

10 m in diameter. PM10 measurements contain both fine (PM2.5) and coarse 

particles. In 2006, the U.S. EPA revoked the annual PM10 standard because the 

available evidence did not suggest a link between long-term exposure to PM10 

and health problems. The 24-hour PM10 NAAQS was retained as well as 
61

minimum monitoring requirements for PM10 based on MSA population and 

PM10 design value as specified in 40 CFR § 58 Appendix D. 

To meet this requirement, size-selective inlet high-volume samplers are operated 

at 22 sites to meet the requirements for PM10 FRM sampling. In addition PM10 

continuous FEM analyzers are operated at 14 sampling sites providing hourly 

particulate concentration measurements. Figure 13 shows the spatial distribution 

of the sampling sites. Real-time monitors, for the most part, are clustered in the 

high concentration areas, with two located in the desert area where wind-blown 

crustal material can cause exceedances of the twenty-four hour standard during 

high wind events. Real time PM10 monitors also support ongoing health studies 

in the region. All PM10 FRM monitors currently operate on a one-in-six day 

schedule with the exception of Indio and Rubidoux, the maximum concentration 

sites in each air basin, which operate on an enhanced frequency one-in-three day 

schedule as required by 40 CFR § 58.12(e). The continuous PM10 FEM monitors 

also provide a daily record of PM10 values at many of the higher concentration 

sites. 

Monitoring Objective

The majority of the PM10 sites are designated as population exposure sites as 

shown in Table 28. The 2007-2008 data shows that Mira Loma (Van Buren) 

reported the highest concentrations in the South Coast Basin at 142 and 135 

g/m3in 2007, and 2008 respectively (excluding exceptional events). This site 

began operation in 2006, and previous to that, Rubidoux was designated as the 

maximum concentration site requiring enhanced monitoring frequency as per 40 

CFR § 58.12(e) based on 2000-2005 monitoring data. This assessment concludes 

that based on recent years monitoring data, Mira Loma will be designated the 

maximum concentration site and the required enhanced monitoring frequency will 

be provided by a continuous PM10 FEM BAM recently installed at the site. The 

remainder of the PM10 sites are consistent with population exposure at the 

neighborhood scale. Figure 14 shows the distribution of the PM10 monitors 

along with the population change from 1990 through 2009. Sites are concentrated 

inland, where particulate concentrations tend to be higher. 
62

Spatial Scale of Representativeness

The vast majority of sites showed consistency between the spatial scale of 

representativeness and monitoring objective. The North Long Beach site was 

designated at the middle scale but with a population-oriented monitoring 

objective. Population-oriented sites are more consistent with the neighborhood 

scale of representativeness.

Correlation Analysis

PM10 correlation analysis for data collected during 2008 between sites in Los 

Angeles, Orange, Riverside, and San Bernardino counties are shown in Figure 15. 

Site pairs with correlations greater than 0.8 and relative differences less than 0 .3 

for PM10 are:

060370002 (Azusa) with 060710025 (Ontario)

Station Monitoring objective Spatial Scale Site consistent with 

monitoring objective

Perris Population oriented Neighborhood Yes

Anaheim Population oriented Neighborhood Yes

Azusa Population oriented Neighborhood Yes

Banning Population oriented Neighborhood Yes

Burbank Population oriented Neighborhood Yes

Crestline Population oriented Neighborhood Yes

Fontana Population oriented Neighborhood Yes

Glendora Population oriented Neighborhood Yes

Indio Population oriented Neighborhood Yes

Lake Elsinore Population oriented Neighborhood Yes

LAX Hastings Population oriented Neighborhood Yes

Long Beach (North) Population oriented Neighborhood Yes

Los Angeles (Main St.) Population oriented Neighborhood Yes

Mira Loma (Jurupa) Population oriented Neighborhood Yes

Mira Loma (Van Buren) High Concentration Neighborhood Yes

Mission Viejo Population oriented Neighborhood Yes

Norco Population oriented Neighborhood Yes

Ontario (Fire-Station) Population oriented Neighborhood Yes

Palm Springs Population oriented Neighborhood Yes

Redlands Population oriented Neighborhood Yes

Rubidoux Population oriented Neighborhood Yes

San Bernardino Population oriented Neighborhood Yes

Santa Clarita Population oriented Neighborhood Yes

Long Beach (South) Population oriented Neighborhood Yes

Temecula TBD TBD TBD

Upland Population oriented Neighborhood Yes

TABLE 28 PM10 Network Design
63

060370016 (Glendora) with 060711004 (Upland)

060658001 (Rubidoux) with 060658001 (Norco)

0600658005 (Mira Loma VB) with 060658001 (Rubidoux)

060712002 (Fontana) with 060710025 (Ontario)

060719004 (San Bernardino) with 060712002 (Fontana)

This analysis shows that for PM10, few sites correlate in low concentration areas. 

The greatest correlation was found between Rubidoux and Mira Loma (Van 

Buren), the two sites with the highest 24-hour PM10 concentrations in the Basin.

Minimum Number of Sites Required

EPA criteria specify the minimum number of sites required in an air monitoring 

network based on MSA population and design value. Population data was taken 

from the 2000 census to determine the required number of samplers for the SCAB 

and are shown in Table 29. The information shows that the South Coast AQMD

air monitoring network significantly exceeds the minimum required number of 

samplers for PM10. 

Table 29 Minimum PM10 Requirement

MSA Min. # 

Monitors 

Required

# 

Monitors 

Active

31100 2 9

40140 3 16

PM2.5

Particulate matter, also known as particle pollution or PM, is a complex mixture of 

extremely small particles and liquid droplets. Particle pollution is made up of a number 

of components, including ions (such as nitrates and sulfates), organic chemicals, 

elemental carbon, metals, and soil or dust particles. Fine particles, such as those found in 

smoke and haze, are 2.5 m in diameter and smaller. These particles can be directly 

emitted from sources such as mobile sources, meat cooking and forest fires, or they can 

form when gases emitted from power plants, industries, and automobiles react in the air.

Regulatory Requirement

The nation's air quality standards for particulate matter were first established in 

1971 and were not significantly revised until 1987, when the EPA changed the 

indicator of the standards to regulate inhalable particles smaller than or equal to 

10 um in diameter. Ten years later, after a lengthy review, the EPA revised the 

PM standards, setting separate standards for fine particles (PM2.5) based on their 

link to serious health problems including increased symptoms, hospital 

admissions, emergency room visits, and premature death for people with heart 
64

and lung disease. The regulation also required local agencies to operate a 

minimum number of PM2.5 monitoring sites as specified in 40 CFR § 58 

Appendix D.

To comply with regulatory requirements, a network of 17 Federal Reference 

Method (FRM) samplers was first deployed in early 1999. In December 1999, a 

second Coachella Valley PM2.5 sampling site was established in Palm Springs. 

On June 20, 2003, PM2.5 sampling began at the South Long Beach location. The 

final addition to the PM2.5 FRM network occurred in October 2005 at the newly 

established Mira Loma (Van Buren) site. The current number of PM2.5 FRM 

sampling sites remains at 20 and is depicted in Figure 16.

Prior to 2009, a network of continuous PM2.5 monitors was in operation, 

although they did not have FEM status. In January 2009, a network of seven 

PM2.5 FEM monitors were deployed and designated as Special Purpose Monitors 

(SPM) in order to provide time for comparison to collocated FRM samplers. The 

two-year maximum SPM status expires at the end of 2010 and comparability 

analysis will be completed before that time. A network of ten non-FEM PM2.5 

continuous monitors continues operation. 

Monitoring Objective

The PM2.5 monitoring network is shown in Figure 17 along with population trend 

from 1999 through 2009. Most PM2.5 sites are designated as population 

exposure at the neighborhood scale. Review of 2008 data shows that Central Los 

Angeles, Anaheim, Pasadena, South Long Beach, Rubidoux, Burbank, and North 

Long Beach recorded the highest concentrations of PM2.5. The lowest value 

recorded was at the Palm Springs monitoring location, which is more consistent 

with a regional transport site rather than a population-oriented site. 
65

Spatial Scale of Representativeness

All PM2.5 spatial scales of representativeness were consistent with the 

monitoring objectives as shown in Table 30.

Correlation Analysis

PM2.5 correlation for 2008 between sites in Los Angeles, Orange, Riverside, and 

San Bernardino counties are shown in Figure 18. Data for 2008 was used because 

it was the most recent complete data set for the South Coast AQMD PM2.5 

monitoring network. Site pairs with correlations greater than 0.8 and relative 

differences less than 0.3 for PM2.5 are:

060370002 (Azusa) with 060372005 (Pasadena)

060658001 (Rubidoux)

060374002 (North Long Beach) with 060374004(South Long Beach)

060651003 (Riverside Magnolia) with 060658001 (Rubidoux)

Station Monitoring objective Spatial Scale Site consistent with 

monitoring objective

Anaheim Population oriented Neighborhood Yes

Azusa Population oriented Neighborhood Yes

Big Bear Population oriented Neighborhood Yes

Burbank Population oriented Neighborhood Yes

Compton Population oriented Neighborhood Yes

Crestline Population oriented Neighborhood Yes

Fontana Population oriented Neighborhood Yes

Glendora Population oriented Neighborhood Yes

Indio Population oriented Neighborhood Yes

Lake Elsinore Population oriented Neighborhood Yes

Long Beach (North) High concentration Neighborhood Yes

Los Angeles (Main St.) High concentration Neighborhood Yes

Mira Loma (Van Buren) Population oriented Neighborhood Yes

Mission Viejo Population oriented Neighborhood Yes

Ontario (Fire-Station) Population oriented Neighborhood Yes

Palm Springs Population oriented Neighborhood Yes

Pasadena Population oriented Neighborhood Yes

Pico Rivera Population oriented Neighborhood Yes

Reseda Population oriented Neighborhood Yes

Riverside Population oriented Neighborhood Yes

Rubidoux High concentration Neighborhood Yes

San Bernardino Population oriented Neighborhood Yes

Santa Clarita Population oriented Neighborhood Yes

Long Beach (South) Population oriented Neighborhood Yes

Upland Population oriented Neighborhood Yes

TABLE 30 PM2.5 Network Design
66

060710025 (Ontario) with 060712002 (Fontana)

060712002 (Fontana) with 060719004 (San Bernardino)

This analysis shows that for PM2.5, a number of clusters have a high level of 

correlation and a low average relative difference.

Minimum Number of Sites Required

EPA criteria specify minimum numbers of sites required in an air monitoring 

network based on MSA population and measured concentrations. Population data 

was taken from the 2000 census to determine the required number of samplers for 

the SCAB and are shown in Table 31. The information shows that the South 

Coast AQMD air monitoring network exceeds the required minimum numbers of 

samplers for PM2.5. 

Table 31 Minimum PM2.5 Requirement

MSA

Minimum 

Number of 

Monitors 

Required

Number of 

Monitors 

Active

31100 6-10 12

40140 6-10 11
67

Figure 2 South Coast AQMD O3 Monitoring Locations
68

Figure 3 O3 Monitoring Locations and Change in Population 1990 Through 2009
69

Figure 4 2008 Los Angeles, Orange, Riverside, and San Bernardino County O3 Site Correlation
70

Figure 5 South Coast AQMD Monitoring Locations for CO
71

Figure 6 CO Monitoring Locations and Change in Population 1990 Through 2009
72

Figure 7 South Coast AQMD Monitoring Locations for NO2
73

Figure 8 NO2 Monitoring Locations and Change in Population 1990 Through 2009
74

Figure 9 South Coast AQMD Monitoring Locations for SO2
75

Figure 10 SO2 Monitoring Locations and Change in Population 1990 Through 2009
76

Figure 11 South Coast AQMD Source and Ambient Pb Monitoring Locations
77

Figure 12 Pb Monitoring Locations and Change in Population 1990 Through 2009
78

Figure 13 South Coast AQMD PM10 Monitoring 

Locations
79

Figure 14 PM10 Monitoring Locations and Change in Population 1990 Through 2009
80

Figure 15 2008 Los Angeles, Orange, Riverside, and San Bernardino County PM10 

correlation
81

Figure 16 South Coast AQMD PM2.5 Monitoring Locations B = BAM FEM

B1 = BAM
82

Figure 17 PM2.5 Monitoring Locations and Population Change 1999 Through 2009
83

Figure 18 2008 Los Angeles, Orange, Riverside, and San Bernardino County PM2.5 

correlation
84

Analysis Issue Conclusion

Network Design

O3 Monitoring Objective

Crestline, Fontana, Santa Clarita, San Bernardino, 

Glendora, Upland, Redlands & Banning are consistent 

with High Concentration sites.

O3 Monitoring Objective

LAX Hastings and North Long Beach values are 

consistent with background levels

O3 Monitoring Objective

The remainder of the sites are consistent with 

Population exposure at neighborhood or urban level 

scale of representativeness; sites in the western 

portion should be examined for their data value

CO Monitoring Objective

Lynwood and Anaheim values are consistent with 

high concentration sites. Lynwood was closed during 

2008 and moved to Compton.

CO Monitoring Objective

Palm Springs, Lake Elsinore, Santa Clarita, and Mission 

Viejo sites are more consistent with background 

concentrations

CO Monitoring Objective

The remainder of the sites are consistent with 

population exposure at the neighborhood scale of 

representativeness; sites in the western portion should 

be further examined for their data value

NO2 Monitoring Objective

North Long Beach, Lynwood and Central LA are 

consistent with high concentration monitoring sites. 

Lynwood closed in 2008 and was relocated to 

Compton

NO2 Monitoring Objective

Palm Springs and Lake Elsinore are consistent with 

background concentrations

NO2 Monitoring Objective

The remainder of the sites are consistent with 

population exposure; sites in the western portion 

should be examined for their data value

SO2 Monitoring Objective

North Long Beach remains consistent with a high 

concentration site; the remainder of sites should be 

further examine for data value

PM10 Monitoring Objective

Mira Loma (Van Buren), Indio, Rubidoux, Azusa, Santa 

Clarita, and Ontario (Fire Station). Are consistent with 

high concentration monitoring sites 

PM10 Monitoring Objective

Crestline, Mission Viejo, and LAX Hastings are 

consistent with background concentrations

PM10 Monitoring Objective

The remainder of the sites are consistent with 

population exposure at the neighborhood scale of 

representativeness.

PM2.5 Monitoring Objective

Central Los Angeles, Anaheim, Pasadena, South Long 

Beach, Rubidoux, Burbank and North Long Beach are 

consistent with their current designation as high 

concentration sites 

PM2.5 Monitoring Objective

Palm Springs is consistent with background 

concentrations

TABLE 32 Summary Table
85

Analysis Issue Conclusion

Pb Monitoring Objective

North Long Beach population oriented monitoring 

objective is not consistent with micro scale 

representation, is more consistent with a high 

concentration monitoring objective at microscale

Pb Monitoring Objective

All sites should be examined further for their data 

value

Correlation Matrix O3

Azusa & Glendora/Pomona/Pasadena/Upland/Fontana 

O3 correlation > .8 & relative difference < .3

Correlation Matrix O3

Glendora & Pomona/Pasadena/Upland/Fontana O3 

correlation > .8 & relative difference < .3

Correlation Matrix O3

Burbank & Central LA/Pasadena O3 correlation > .8 & 

relative difference < .3

Correlation Matrix O3

Central LA & Pico Rivera/Pasadena O3 correlation > .8 

& relative difference < .3

Correlation Matrix O3

Pomona & Upland/Fontana O3 correlation > .8 & 

relative difference < .3

Correlation Matrix O3

Anaheim & La Habra O3 correlation > .8 & relative 

difference < .3

Correlation Matrix O3

Banning Airport & Tribal site O3 correlation > .8 & 

relative difference < .3

Correlation Matrix O3

Rubidoux & Fontana/Redlands/San Bernardino O3 

correlation > .8 & relative difference < .3

Correlation Matrix O3

Upland & Fontana O3 correlation > .8 & relative 

difference < .3

Correlation Matrix O3

Fontana & Redlands/San Bernardino O3 correlation > 

.8 & relative difference < .3

Correlation Matrix O3

Redlands & San Bernardino O3 correlation > .8 & 

relative difference < .3

Correlation Matrix PM2.5 Burbank and Pasadena > .8 & relative difference < .3

Correlation Matrix PM2.5 Central LA & Pasadena > .8 & relative difference < .3

Correlation Matrix PM2.5

Riverside Magnolia & Fontana/San 

Bernardino/Rubidoux > .8 & relative difference < .3

Correlation Matrix PM2.5

Fontana & San Bernardino > .8 & relative difference < 

.3

Correlation Matrix PM2.5

San Bernardino & Rubidoux > .8 & relative difference < 

.3

Correlation Matrix PM2.5 Rubidoux & Mira Loma Van Buren > .8 & relative 

difference < .3

Correlation Matrix PM10

Azusa & Glendora/Ontario > .8 & relative difference < 

.3

Correlation Matrix PM10 Glendora & Upland > .8 & relative difference < .3

Correlation Matrix PM10 Norco & Rubidoux > .8 & relative difference < .3

Correlation Matrix PM10

Rubidoux & Mira Loma Van Buren > .8 & relative 

difference < .3

Correlation Matrix PM10 Ontario & Fontana > .8 & relative difference < .3

Correlation Matrix PM10 Fontana & San Bernardino > .8 & relative difference < 

.3

Minimum number of sites required Gaseous Criteria Pollutants

South Coast AM network exceeds minimum number of 

sites required for O3, CO, NO2, & SO2

Minimum number of sites required Particulate Criteria Pollutants

South Coast AM network exceeds minimum number of 

sites required for PM2.5, PM10, & Pb

TABLE 32 Summary Table (cont)
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IV. POTENTIAL SOUTH COAST AQMD NETWORK CHANGES 

AND RECOMMENDATIONS

OVERVIEW

This section describes potential changes to the South Coast AQMD air monitoring network that 

would help to address the findings of the site-by-site assessments (Section II) and the pollutant 

network assessments (Section III). The overall goal of these potential modifications to the 

network design is to improve the ability to achieve multiple monitoring objectives while 

ensuring the efficient use of resources.

Note that the current AQMD air monitoring network meets or exceeds U.S. EPA monitoring 

requirements and satisfies multiple monitoring purposes. The dense network of monitoring 

locations covering a wide area provides the necessary data for NAAQS attainment decisions. It 

also provides a robust data set for air quality model validation, trend analysis, health studies, and 

real-time public communication of air quality status. The AQMD places a high value on all 

these monitoring purposes, all of which must be carefully considered before network changes are 

made. 

Many of the findings described in the previous sections are site-specific issues that are addressed 

by South Coast AQMD on an ongoing basis. These include site infrastructure improvements and 

alterations such as vegetation trimming, soil stabilization or paving, replacement of shelters, 

moving probes and inlets to meet appropriate setback criteria, and increasing or improving power 

supplies. Through the Annual Network Plan and regular audit and maintenance schedules, issues 

such as these are continually being identified and addressed. However, when such issues cannot 

be addressed due to logistical constraints, then the value and monitoring objectives of a 

particular site could be reconsidered. Furthermore, the monitoring objectives and spatial scales 

of all sites are assessed as part of the Annual Network Plan, ensuring U.S. EPA minimum 

monitoring requirements are satisfied. Therefore, relatively minor changes to site infrastructure 

and monitoring objective/spatial scale designations are not explicitly addressed in this section, 

although these factors are important in determining the value of a site within a larger pollutant 

monitoring network.

What follows are some potential network modifications that address larger issues such as 

redundancies, gaps, efficiencies, and synergies within and between the South Coast AQMD

pollutant monitoring networks. A summary of recommended network modifications to the South 

Coast AQMD monitoring network is provided at the end of this section. Note that there are 

many purposes for air quality monitoring, some beyond those described in this assessment. 

Closing, moving or creating monitoring sites requires significant resources and often a long 

period of concurrent monitoring to show comparability. Thus, these suggestions must be 

weighed against many other factors before being implemented.

SO2, NO2, AND CO MONITORING NETWORKS

The South Coast AQMD monitoring network far exceeds the minimum monitoring requirements 

for SO2, NO2, and CO, and South Coast AQMD areas are currently in attainment of the NAAQS 
87

for these pollutants. As of 2009, there were no minimum monitoring requirements for these 

criteria pollutants. In 2010, minimum monitoring requirements were added for NO2 and SO2, 

and these new regulations will require changes to the NO2 network by 2013. New NAAQS and 

monitoring regulations for CO are also anticipated with possible network modifications required. 

In all cases, South Coast AQMD measurements of SO2, NO2, and CO are made at monitoring 

sites that are also part of the more essential O3 and PM monitoring networks for which the basin 

is not in attainment with the NAAQS. Thus, the cost of continuing to monitor for these 

pollutants is relatively low given that the site infrastructure and staff resources dedicated to the 

sites will continue as part of the PM and O3 networks. However, there are costs associated with 

the maintenance, calibration, replacement, and auditing of the SO2, NO2, and CO instruments as 

well as the resources required to validate and submit the data to U.S. EPA. 

Given the recent and upcoming revisions to monitoring regulations for these pollutants, a 

reduction in the number of SO2, NO2, and CO monitors in the network is not recommended until 

network design decisions to meet the new requirements have been made. For instance, new NO2 

sites will be needed near roadways and possibly in EJ areas. The shifting of resources to 

accommodate these new requirements will affect the current network configuration.

Once the new regulations for CO are final and network design decisions for NO2 and SO2 have 

been made, a reconsideration of the extent of the SO2, NO2, and CO networks is recommended. 

It is likely that the future South Coast AQMD monitoring networks for these pollutants will 

continue to exceed minimum requirements in order to meet other objectives such as model 

validation, maintenance plan requirements, and trend analysis. A careful consideration of these 

factors along with the costs of continued operation may lead to more efficient and effective 

monitoring networks for SO2, NO2, and CO.

OZONE MONITORING NETWORK

South Coast AQMD exceeds the minimum monitoring requirements for the O3 monitoring 

network. Due to the large population in Southern California and the complexity of the 

geography and meteorology, a relatively large number of air monitoring stations are needed to 

adequately describe air quality in South Coast AQMD’s jurisdiction and provide important 

health information to the public. Both South Coast AQMD air basins (South Coast and 

Coachella Valley) are designated non-attainment for O3, and a wide, robust O3 network is 

critical for accurate assessment and modeling efforts.

However, as a regional pollutant, O3 concentrations generally do not vary significantly on short 

spatial scales, the exception being near busy roadways where NO titration occurs. Based on the 

correlation analysis in Section III, some sites in close proximity to one another provide very 

similar O3 readings. Three clusters of high similarity identified in Section III were:

 Fontana/Redlands/San Bernardino/Rubidoux

 Azusa/Glendora/Pomona/Upland/Fontana
88

 Anaheim/La Habra

In terms of siting criteria, findings related to these sites included: 

 La Habra - is within 3 m of cypress trees surrounding inlet probe and does not meet 

distance from traffic lane requirement.

 Pomona - is less than the required distance from roadway.

Other assessment findings regarding these sites include:

 Glendora has been in operation for 30 years and was originally a CARB monitoring 

location. There have been difficulties securing a long-term rental contract and the City of 

Glendora requirements have made it difficult to upgrade the monitoring shelter. The site 

lacks adequate space and infrastructure to expand at the current location. 

 La Habra has been in operation for 50 years; however, it lacks adequate space and 

infrastructure to expand to include particulate monitoring. The site has not typically been 

used for research or air toxics studies and there are few synergies at the site between air 

monitoring programs. 

 Pomona has been in operation for 45 years; however, it lacks adequate space and 

infrastructure to expand. The data has not typically been used for research or air toxics 

studies and the site was originally intended as a micro-scale CO location. There are few 

synergies between air monitoring programs at this location.

The Fontana/Redlands/San Bernardino/Rubidoux cluster is well spaced in an area of generally 

the highest O3 levels in the basin. It is important to continue to monitor in this area and have a 

good spatial distribution of O3 levels given the frequent exceedances and need for public health 

advisories. Therefore, no changes are recommended to these O3 sites.

The Azusa/Glendora/Pomona/Upland cluster (excluding the more distant site Fontana) is 

geographically compact showing high degree of comparability in O3 measurements. In 2007 

and 2008, Upland recorded the most exceedances of federal and state air quality standards of O3, 

although this area is no longer the highest O3 region in the basin. The Glendora site is only 

seven km from the Azusa site, and although it can record higher O3 levels than Azusa, readings 

are typically lower than Upland. The Pomona site is also relatively close to both Upland and 

Azusa. Upland and Azusa have been active sights for 37 and 53 years respectively providing the 

needed long-term trends. Given the proximity to other correlated stations and the siting and 

infrastructure issues mentioned above, both Glendora and Pomona could be considered 

potentially redundant in terms of O3 measurements.

The Anaheim/La Habra cluster show similar but relatively low levels of O3 according to recent 

data and the correlation analysis. Given these low levels, the unresolvable siting issues, and the 

few other measurements made at La Habra (CO and NO2 only), this site would be another 

potential candidate for reduction in size of the O3 network.
89

If O3 measurements cease at both La Habra and Pomona, a geographical gap might be created in 

northwestern Orange County. South Coast AQMD headquarters in Diamond Bar is at the center 

of that gap, and a new site at headquarters would fill the potential need for additional O3 

measurements in the area while providing considerable efficiencies with a convenient location. 

Two other changes to the O3 network are already underway. First, the Mira Loma Van Buren 

monitoring location was established as a replacement site for the Mira Loma Jurupa monitoring 

location. Ozone data for Jurupa was not included in the correlation analysis as it is not in the 

AQS database. The closure of the Jurupa station is planned within the coming year. Second, a 

new site in Temecula is already in place with O3 measurements planned. It is in an area that has 

grown significantly in recent years and may not be adequately represented by the current O3 

monitoring network.

PM2.5 MONITORING NETWORK

The South Coast AQMD monitoring network exceeds the minimum monitoring requirements for 

PM2.5. Due to the large population in Southern California, the complexity of the geography, 

and the non-attainment status of the basin, a relatively large number of air monitoring stations 

are needed to adequately describe air quality and provide important health information to the 

public.

As a generally regional pollutant, PM2.5 concentrations generally do not vary significantly on 

short spatial scales unless very near strong sources of particulate matter. Based on the 

correlation analysis in Section III, some sites in close proximity to one another provide very 

similar PM2.5 readings. Two clusters of high similarity identified in Section III were:

 San Bernardino/Rubidoux/Fontana

 North Long Beach/South Long Beach

In terms of siting criteria, findings related to these sites included: 

 Fontana is within 9 m of unpaved parking and within 9 m of regularly idling diesel 

exhaust.

 South Long Beach does not currently meet all 40 CFR § 58 Appendix E Probe Siting

Criteria, specifically the spacing from obstructions surrounding the instrumentation.

Other assessment findings regarding these and other sites include:

 Big Bear Lake has been in operation for 11 years and was originally established to 

determine the extent of winter wood smoke particulate matter. Since that time, there 

have not been exceedances of the standard. It is the only measurement made at the site 

and thus there are no synergies between monitoring programs. Consideration must be 

given to the remoteness of the location and the cost to maintain the site.
90

 Fontana has been in operation for 29 years. However, the site lacks adequate space and 

infrastructure to expand at the current location.

 South Long Beach was established June 2003 to monitor particulate influence from port 

activities. The infrastructure of the facility meets the needs of particulate sampling, but 

there are no facilities for continuous analyzers and no room for expansion. There are no 

synergies between air monitoring programs or use of office space by inspectors. The cost 

to relocate the site is low due to the low number of samplers and there is potential to 

move this site to a location nearer to port activities.

The San Bernardino/Rubidoux/Fontana cluster is relatively well spaced in an area of generally 

the highest PM2.5 levels in the basin. It is important to continue to monitor in this area and 

have a good spatial distribution of PM2.5 levels given the frequent exceedances and need for 

public health advisories. Despite some potential siting issues at Fontana, no changes are 

recommended to these PM2.5 sites.

The North Long Beach/South Long Beach cluster is geographically compact with only four 

miles separating the sites. Data at the two sites is similar in terms of correlation, exceedances, 

averages, and maximum levels. The South Long Beach location was intended to measure the 

impact of the nearby port activities. However, no site closer to the Port area could be secured at 

the time. In 2007, a site for a temporary air monitoring study was secured much closer to Port 

activities, and this site is still available to be made permanent with sufficient infrastructure for 

expansion. Given the limitations of the current South Long Beach site with no room for gaseous 

measurements, and the original intended purpose of the site, the temporary site on Anaheim 

Street in Long Beach may be a better option. Therefore, a potential modification of the PM2.5 

network is to move the South Long Beach measurements to this new site closer to the Port 

activities. Concurrent monitoring may need to be conducted to show that the new site records 

similar or higher PM2.5 levels than the current site.

The Big Bear Lake monitoring location only measures PM2.5, and has not been in violation of 

the 24-hour or annual PM2.5 NAAQS in 2007 or 2008. Sampling only occurs on a reduced, U.S. 

EPA approved, sampling frequency of one-in-six day due to the remote location. The original 

intent of the site was to determine if wintertime residential wood burning could lead to NAAQS 

violations. Given that violations have not been observed and that the remote location of the site 

requires significant staff resources to maintain even at the reduced sampling schedule, the value 

of the site should be reconsidered. 

Another suggested change in the configuration of the PM2.5 network is to continue the transition 

to continuous PM2.5 FEM monitors. Currently, these monitors are being run collocated with 

FRM filter-based measurements to establish comparability and determine any biases. Once 

complete, the FEM continuous monitors can replace many existing FRM monitors in the 

network. This will reduce the considerable resources required to maintain the aging FRM 

samplers and to process and weigh the collected filter samples. It will also provide for daily 

data at sites that may only be one-in-three day sites currently, and it will provide useful hourly 

data for public reporting and air quality assessments. 
91

PM10 MONITORING NETWORK

The South Coast AQMD monitoring network exceeds the minimum monitoring requirements for 

PM10. Due to the large population in Southern California, the complexity of the geography, and 

the current non-attainment status of the basin, a relatively large number of air monitoring stations 

are needed to adequately describe air quality and provide important health information to the 

public.

PM10 includes PM2.5, but concentrations can vary significantly on short spatial scales. 

However, based on the correlation analysis in Section III, some sites in close proximity to one 

another provide similar PM10 readings. These sites tend to be in the highest concentration areas 

(Rubidoux and Mira Loma Van Buren), but the correlated site clusters are not as clear as for O3 

and PM2.5. 

In terms of siting criteria, findings related to PM10 sites include: 

 South Long Beach does not currently meet all 40 CFR § 58 Appendix E Probe Siting 

Criteria, specifically the spacing from obstructions surrounding the instrumentation.

Other assessment findings regarding these and other sites include:

 Norco has been in operation for 30 years. The infrastructure is inadequate as there are no 

indoor facilities which allow for monitoring of criteria pollutants. Data is not used for 

purposes other than NAAQS and there are no other measurements being made at the site. 

 Ontario Fire Station –has been in operation for 11 years. The infrastructure is inadequate 

as there are no indoor facilities which allow for monitoring of criteria pollutants. Data 

are not used for purposes other than NAAQS and there are no synergies between 

programs.

Given the high levels of PM10 recorded at both Rubidoux and Mira Loma, no changes are 

recommended for PM10 measurements at these sites, despite their high level of correlation. 

However, given that Mira Loma has consistently recorded higher levels of PM10 over the last 

five years than Rubidoux, the Mira Loma site should be designated as the expected maximum 

concentration PM10 site as per 40 CFR § 58.12(e).

The only measurement at the Norco site is PM10 and thus does not provide any synergies with 

other programs. It consistently records lower PM10 concentrations than nearby Rubidoux and 

Mira Loma. Therefore, it can be considered for potential elimination from the PM10 monitoring 

network. A similar analysis can be made for the Ontario station, with few synergies with other 

programs and very similar PM10 statistics levels to Norco and other nearby sites. If both sites 

were eliminated, this may create a geographical gap in western Riverside and San Bernardino 

Counties. To provide spatial coverage in that area, the sites could be consolidated into a new 

location with better infrastructure between the current Norco and Ontario sites. 
92

The potential move of the South Long Beach site closer to port activities suggested for the 

PM2.5 network also holds for the PM10 network. 

Another suggested change in the configuration of the PM10 network is to transition towards 

continuous PM10 FEM monitors. New continuous PM10 monitors have recently been deployed 

for a regional health study and can eventually serve to replace many existing FRM monitors in 

the network. This will reduce the considerable resources required to maintain the aging FRM 

samplers and to process and weigh the collected filter samples. It will also provide for daily 

data at sites that may only be one-in-six day sites currently, and it will provide useful hourly data 

for public reporting and air quality assessments.

SUMMARY OF RECOMMENDED NETWORK MODIFICATIONS

The current AQMD air monitoring network meets or exceeds U.S. EPA monitoring requirements 

while satisfying a wide array of monitoring purposes, some beyond those described in this 

assessment. Meeting minimum monitoring requirements is just one factor in determining the 

value of sites and measurements. Given the challenges of meeting air quality standards in 

Southern California and the need for information to help in developing control strategies to 

achieve attainment, the South Coast AQMD monitoring network will continue to far exceed the 

minimum requirements. Furthermore, closing, relocating or creating monitoring sites requires 

significant resources and often a long period of concurrent monitoring to show comparability. 

Thus, the suggestions summarized below must be weighed against many other factors before 

being implemented. Most changes to the monitoring network are subject to approval by the U.S. 

EPA Regional Administrator.

 Once new monitoring regulations, attainment status, and network decisions are known for 

SO2, NO2, and CO, consider a general reduction in the number of sites monitoring for 

those pollutants in the network while still meeting all monitoring objectives and 

purposes.

 Reconsider the values of the Glendora, La Habra and Pomona sites, and potentially 

consolidate measurements at nearby sites or at a new site in Diamond Bar.

 Reconsider the value of the Big Bear Lake PM2.5 site.

 Consider moving all South Long Beach measurements to a new permanent site on 

Anaheim Street in Long Beach that is closer to port activities and will better achieve the 

original purpose of the site.

 Reconsider the value of the Norco and Ontario particulate sites, and potentially 

consolidate measurements at nearby sites or at a new site between the two.

 Continue to transition to continuous PM measurements that can eventually replace filterbased measurements.